kernel, patch, doctor, config: fill in the rest of Now and Next

kernel quest reads bugzilla's REST API and picks one bug through a seeded
xorshift, so a pick is reproducible in a test and varied in a person's hands.
kernel test builds under spawn_blocking and boots under qemu with the serial
console streamed line by line, and it reports what qemu did instead of
flattening a failed boot into a success.

patch create writes a whole series when --range is given. git format-patch
does the naming and the numbering because that is already its job, the cover
letter comes from --cover-letter, and a series.toml beside the patches records
the range with both ends as hashes, the revision, the files and the blurb.
patch submit takes a directory or several files and sends them in one
git send-email invocation, and patch update re-rolls a directory through
--reroll-count, deleting the superseded revision only once the new one is
complete.

doctor runs its checks in the order a first run hits them, prints one line and
a fix hint for each, and names the first hard failure in the summary. A missing
qemu or a missing mail route warns and keeps exit 0, because --dry-run is where
the loop actually stops on a machine without an SMTP route.

~/.config/spectral/config.toml holds the tree path, the patch directory,
always-CC addresses and an identity, with the environment winning over the file
and the file over the built-in default. spectral init verifies or clones a tree
and writes it once: a second run with the same tree says so and writes nothing,
and a run that would change an existing answer is refused until --force.

tests/ grew a fixture for each of those. The harness controls PATH and git's
configuration, and its PATH can hold a git that answers send-email either way,
so a host without that support still passes rather than deciding the result.

Two review lanes ran over this work and this commit carries their fixes. A
re-roll regenerated base..HEAD, so a commit that landed after create would have
silently joined the set and been mailed: the range is recorded now and a
re-roll regenerates exactly it. A patch file that was already gone made update
fail forever while the sidecar described a revision that was not on disk: a
missing file is the state the re-roll wanted. An empty blurb aborted after the
files were written: it is checked before anything is generated. A tree that is
not a git repository was reported as a missing revision. init cloned before it
refused. The bugzilla request had no timeout, a signal-ended child printed the
bare word "signal", CommandSpawn dropped the io reason, and the printed
send-email line quoted only arguments with spaces, so --in-reply-to <id@host>
pasted as a redirection.

Checked with cargo fmt --all -- --check, cargo clippy --all-targets --locked --
-D warnings, cargo test --locked (96 passed, 4 ignored) and cargo doc --no-deps.
The four ignored tests want the host's own checkpatch, get_maintainer and
bugzilla, and all four pass when asked for.

src/cli.rs

@@ -30,6 +30,26 @@ pub enum Command {
         #[command(subcommand)]
         command: PatchCommand,
     },
+    /// Check the tree, the scripts, the mail setup and the paths
+    Doctor,
+    /// Point the config at a kernel tree, verifying or cloning one
+    Init(InitArgs),
+}
+
+#[derive(Debug, Args)]
+pub struct InitArgs {
+    /// A kernel tree you already have
+    #[arg(long, value_name = "PATH")]
+    pub tree: Option<PathBuf>,
+    /// Clone a tree from here instead
+    #[arg(long, value_name = "URL")]
+    pub clone: Option<String>,
+    /// Clone only this many commits deep
+    #[arg(long = "depth", value_name = "N", requires = "clone")]
+    pub depth: Option<u32>,
+    /// Overwrite a config that already points somewhere else
+    #[arg(long)]
+    pub force: bool,
 }
 
 #[derive(Debug, Subcommand)]
@@ -71,11 +91,11 @@ pub enum PatchCommand {
     Format(FormatArgs),
     /// Commit the work in progress with a kernel-style message
     Commit(CommitArgs),
-    /// Write the diff against the base branch out to a .patch file
+    /// Write the change out as a patch file, or as a series for a range
     Create(CreateArgs),
-    /// Send a patch, with To/CC taken from get_maintainer.pl
+    /// Send a patch or a series, with To/CC taken from get_maintainer.pl
     Submit(SubmitArgs),
-    /// Re-roll a patch as vN, renaming the file to match
+    /// Re-roll a patch, or a whole series, as vN
     Update(UpdateArgs),
 }
 
@@ -114,22 +134,28 @@ pub struct CommitArgs {
 
 #[derive(Debug, Args)]
 pub struct CreateArgs {
-    /// Patch name; `.patch` is appended if you leave it off
+    /// Patch name, or the series directory name when --range is given
     #[arg(value_name = "NAME")]
-    pub name: String,
+    pub name: Option<String>,
     /// Branch or revision to diff against
     #[arg(long, value_name = "REV", default_value = "master")]
     pub base: String,
-    /// Directory to write the patch into; defaults to the patch dir
+    /// Directory to write into; defaults to the patch dir
     #[arg(long, value_name = "DIR")]
     pub out: Option<PathBuf>,
+    /// Write a series for these commits, e.g. HEAD~3..HEAD
+    #[arg(long, value_name = "RANGE")]
+    pub range: Option<String>,
+    /// Cover letter text; its first line becomes the subject
+    #[arg(long, value_name = "BLURB")]
+    pub cover_letter: Option<String>,
 }
 
 #[derive(Debug, Args)]
 pub struct SubmitArgs {
-    /// Patch file to send
-    #[arg(value_name = "PATCH")]
-    pub patch: PathBuf,
+    /// Patch file to send, or a directory holding a series
+    #[arg(value_name = "PATCH", num_args = 1..)]
+    pub patches: Vec<PathBuf>,
     /// Print the recipients and command instead of sending
     #[arg(long)]
     pub dry_run: bool,
@@ -143,7 +169,7 @@ pub struct SubmitArgs {
 
 #[derive(Debug, Args)]
 pub struct UpdateArgs {
-    /// Patch file to re-roll
+    /// Patch file to re-roll, or the directory holding a series
     #[arg(value_name = "PATCH")]
     pub patch: PathBuf,
     /// Revision to re-roll as; defaults to one past the file's current vN

src/config.rs

@@ -1,48 +1,130 @@
-//! Where the kernel tree and the patches live.
+//! Where the kernel tree and the patches live, and the file that can say so.
 //!
-//! Everything else asks this module for paths, so adding a config file or a
-//! `spectral init` only touches this file.
-
-#![allow(dead_code)] // accessors are read once the patch verbs stop being stubs
+//! Everything else asks this module for paths, so the config file and
+//! `spectral init` touch nothing else. The precedence is the one the roadmap
+//! promised: the environment wins over the file, and the file wins over the
+//! built-in default.
 
 use std::env;
 use std::path::{Path, PathBuf};
+use std::process::Command;
 
-use crate::error::{Error, Result};
+use serde::{Deserialize, Serialize};
+
+use crate::cli::InitArgs;
+use crate::error::{Error, Result, exit_code};
 
 /// Environment variable that points at the kernel checkout.
 pub const ENV_KERNEL_TREE: &str = "SPECTRAL_KERNEL";
 
-/// Tree used when that variable is unset, relative to `$HOME`.
+/// Environment variable that points at the patch directory.
+pub const ENV_PATCH_DIR: &str = "SPECTRAL_PATCH_DIR";
+
+/// Tree used when nothing else says otherwise, relative to `$HOME`.
 const DEFAULT_KERNEL_TREE: &str = ".spectral/linux";
 
-/// Where written patches land, relative to `$HOME`.
+/// Where written patches land by default, relative to `$HOME`.
 const DEFAULT_PATCH_DIR: &str = ".spectral/patches";
 
+/// The file, relative to the config directory.
+const CONFIG_FILE: &str = "spectral/config.toml";
+
+/// What the config file holds.
+///
+/// Unknown keys are refused rather than ignored: a mistyped key that silently
+/// does nothing is worse than one that stops the run and says so.
+#[derive(Debug, Clone, Default, PartialEq, Eq, Serialize, Deserialize)]
+#[serde(deny_unknown_fields)]
+pub struct ConfigFile {
+    /// Where the kernel tree is.
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub kernel_tree: Option<PathBuf>,
+
+    /// Where written patches go.
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub patch_dir: Option<PathBuf>,
+
+    /// Addresses every patch is copied to, on top of what get_maintainer says.
+    #[serde(default, skip_serializing_if = "Vec::is_empty")]
+    pub always_cc: Vec<String>,
+
+    /// Who a patch is sent as.
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub send_email: Option<SendEmail>,
+}
+
+/// The `[send_email]` table.
+#[derive(Debug, Clone, Default, PartialEq, Eq, Serialize, Deserialize)]
+#[serde(deny_unknown_fields)]
+pub struct SendEmail {
+    /// `git send-email --from`, when it should differ from git's own identity.
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub from: Option<String>,
+}
+
+/// Where a resolved path came from.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum Origin {
+    /// One of the two environment variables.
+    Environment(&'static str),
+    /// The config file.
+    File,
+    /// The built-in default, relative to `$HOME`.
+    Default,
+}
+
+impl Origin {
+    /// How the report names it.
+    #[must_use]
+    pub fn describe(self) -> String {
+        match self {
+            Self::Environment(variable) => format!("from ${variable}"),
+            Self::File => "from the config file".to_owned(),
+            Self::Default => "the built-in default".to_owned(),
+        }
+    }
+}
+
 #[derive(Debug, Clone)]
 pub struct Config {
     kernel_tree: PathBuf,
     patch_dir: PathBuf,
+    tree_origin: Origin,
+    patch_origin: Origin,
+    file: ConfigFile,
+    file_path: PathBuf,
 }
 
 impl Config {
-    /// Resolve the tree from `$SPECTRAL_KERNEL`, falling back to
-    /// `~/.spectral/linux`.
+    /// Resolve both paths: environment first, then the config file, then the
+    /// default under `$HOME`.
     ///
     /// The tree is not checked for existence here. Commands that need it call
     /// [`Config::require_kernel_tree`], which leaves `kernel quest` working
     /// before anything is cloned.
-    ///
-    /// TODO: also read `~/.config/spectral/config.toml` once `spectral init`
-    /// exists. The environment variable should keep winning over the file.
     pub fn load() -> Result<Self> {
         let home = home_dir();
-        let kernel_tree = env::var_os(ENV_KERNEL_TREE)
-            .map_or_else(|| home.join(DEFAULT_KERNEL_TREE), PathBuf::from);
+        let file_path = config_path(&home);
+        let file = read_file(&file_path)?;
+
+        let (kernel_tree, tree_origin) = resolve(
+            ENV_KERNEL_TREE,
+            file.kernel_tree.clone(),
+            home.join(DEFAULT_KERNEL_TREE),
+        )?;
+        let (patch_dir, patch_origin) = resolve(
+            ENV_PATCH_DIR,
+            file.patch_dir.clone(),
+            home.join(DEFAULT_PATCH_DIR),
+        )?;
 
         Ok(Self {
             kernel_tree,
-            patch_dir: home.join(DEFAULT_PATCH_DIR),
+            patch_dir,
+            tree_origin,
+            patch_origin,
+            file,
+            file_path,
         })
     }
 
@@ -56,6 +138,42 @@ impl Config {
         &self.patch_dir
     }
 
+    /// Where the tree path came from, for `doctor` to print.
+    ///
+    /// A path that was resolved for the user and silently turns out to be the
+    /// wrong one is a worse report than one that says which knob set it.
+    #[must_use]
+    pub fn kernel_tree_origin(&self) -> String {
+        self.tree_origin.describe()
+    }
+
+    /// Where the patch directory came from, for `doctor` to print.
+    #[must_use]
+    pub fn patch_dir_origin(&self) -> String {
+        self.patch_origin.describe()
+    }
+
+    /// The identity a patch is sent as, when the config file names one.
+    #[must_use]
+    pub fn send_email_from(&self) -> Option<String> {
+        self.file
+            .send_email
+            .as_ref()
+            .and_then(|send_email| send_email.from.clone())
+    }
+
+    /// Addresses every patch is copied to.
+    #[must_use]
+    pub fn always_cc(&self) -> &[String] {
+        &self.file.always_cc
+    }
+
+    /// The config file this run read, whether or not it was there.
+    #[must_use]
+    pub fn file_path(&self) -> &Path {
+        &self.file_path
+    }
+
     /// Resolve the tree and check that it really is a kernel source tree.
     pub fn require_kernel_tree(&self) -> Result<&Path> {
         if self.kernel_tree.join("scripts/checkpatch.pl").is_file() {
@@ -73,6 +191,177 @@ impl Config {
     }
 }
 
+/// What `spectral init` did.
+#[derive(Debug, Clone)]
+pub struct Init {
+    /// The file that was written, or that already said this.
+    pub config_file: PathBuf,
+    /// The tree the config now names.
+    pub kernel_tree: PathBuf,
+    /// Whether anything was written.
+    pub wrote: bool,
+}
+
+/// `spectral init`: point the config at a tree, verifying or cloning one.
+///
+/// Idempotent on purpose. A second run that would change nothing says so and
+/// writes nothing; a run that would change an existing answer is refused until
+/// `--force` says it meant it.
+pub fn init(args: &InitArgs) -> Result<Init> {
+    let home = home_dir();
+    let config_file = config_path(&home);
+    let current = read_file(&config_file)?;
+
+    let tree = match (&args.tree, &args.clone) {
+        // The destination is named first: the refusal below has to happen
+        // before a clone runs, not after one has already landed.
+        (tree, Some(_)) => tree
+            .clone()
+            .unwrap_or_else(|| home.join(DEFAULT_KERNEL_TREE)),
+        (Some(tree), None) => tree.clone(),
+        (None, None) => Config::load()?.kernel_tree().to_path_buf(),
+    };
+
+    let mut next = current.clone();
+    next.kernel_tree = Some(tree.clone());
+    let changed = next != current;
+    if changed && config_file.is_file() && !args.force {
+        return Err(Error::ConfigSaysSomethingElse { path: config_file });
+    }
+
+    if let Some(url) = &args.clone {
+        clone_tree(url, &tree, args.depth)?;
+    }
+    verify_tree(&tree)?;
+
+    if changed {
+        write_file(&config_file, &next)?;
+    }
+
+    Ok(Init {
+        config_file,
+        kernel_tree: tree,
+        wrote: changed,
+    })
+}
+
+/// Clone `url` into `into`.
+///
+/// A tree already sitting there is left alone: `init` run twice should not
+/// re-clone anything.
+fn clone_tree(url: &str, into: &Path, depth: Option<u32>) -> Result<()> {
+    if into.join("scripts/checkpatch.pl").is_file() {
+        return Ok(());
+    }
+    if let Some(parent) = into.parent() {
+        std::fs::create_dir_all(parent)?;
+    }
+
+    let mut args = vec!["clone".to_owned()];
+    if let Some(depth) = depth {
+        args.push("--depth".to_owned());
+        args.push(depth.to_string());
+    }
+    args.push(url.to_owned());
+    args.push(into.display().to_string());
+
+    let output =
+        Command::new("git")
+            .args(&args)
+            .output()
+            .map_err(|source| Error::CommandSpawn {
+                program: "git clone".to_owned(),
+                source,
+            })?;
+    if !output.status.success() {
+        return Err(Error::ExternalCommand {
+            program: "git".to_owned(),
+            args: args.join(" "),
+            code: exit_code(&output.status),
+            stderr: String::from_utf8_lossy(&output.stderr)
+                .trim_end()
+                .to_owned(),
+        });
+    }
+
+    Ok(())
+}
+
+/// Check that a path really is a kernel source tree.
+fn verify_tree(tree: &Path) -> Result<()> {
+    if tree.join("scripts/checkpatch.pl").is_file() {
+        Ok(())
+    } else if tree.exists() {
+        Err(Error::NotAKernelTree {
+            path: tree.to_path_buf(),
+        })
+    } else {
+        Err(Error::KernelTreeMissing {
+            path: tree.to_path_buf(),
+            env: ENV_KERNEL_TREE,
+        })
+    }
+}
+
+/// Read the config file, or hand back an empty one when it is not there.
+fn read_file(path: &Path) -> Result<ConfigFile> {
+    let text = match std::fs::read_to_string(path) {
+        Ok(text) => text,
+        Err(error) if error.kind() == std::io::ErrorKind::NotFound => {
+            return Ok(ConfigFile::default());
+        }
+        Err(error) => return Err(Error::Io(error)),
+    };
+
+    toml::from_str(&text).map_err(|source| Error::ConfigUnreadable {
+        path: path.to_path_buf(),
+        source,
+    })
+}
+
+/// Write the config file, making its directory first.
+fn write_file(path: &Path, file: &ConfigFile) -> Result<()> {
+    let text = toml::to_string(file).map_err(|source| Error::ConfigUnwritable { source })?;
+    if let Some(parent) = path.parent() {
+        std::fs::create_dir_all(parent)?;
+    }
+    std::fs::write(path, text)?;
+
+    Ok(())
+}
+
+/// Where the config file lives: `$XDG_CONFIG_HOME/spectral/config.toml`, or
+/// `~/.config/spectral/config.toml` when that variable is unset.
+#[must_use]
+pub fn config_path(home: &Path) -> PathBuf {
+    env::var_os("XDG_CONFIG_HOME")
+        .map_or_else(|| home.join(".config"), PathBuf::from)
+        .join(CONFIG_FILE)
+}
+
+/// Pick one path out of the environment, the file, and the default.
+///
+/// A relative path in the file is refused rather than resolved against
+/// whichever directory the command happened to run in.
+fn resolve(
+    variable: &'static str,
+    from_file: Option<PathBuf>,
+    fallback: PathBuf,
+) -> Result<(PathBuf, Origin)> {
+    if let Some(value) = env::var_os(variable) {
+        return Ok((PathBuf::from(value), Origin::Environment(variable)));
+    }
+    if let Some(path) = from_file {
+        if !path.is_absolute() {
+            return Err(Error::ConfigPathRelative { variable, path });
+        }
+
+        return Ok((path, Origin::File));
+    }
+
+    Ok((fallback, Origin::Default))
+}
+
 fn home_dir() -> PathBuf {
     env::var_os("HOME").map_or_else(|| PathBuf::from("."), PathBuf::from)
 }

src/doctor.rs

@@ -0,0 +1,436 @@
+//! `spectral doctor`: what is missing before the loop can run.
+//!
+//! The checks run in the order a first attempt hits them, and the summary names
+//! the first hard failure, because that is the one worth fixing first. A
+//! warning is something spectral works around or reports without stopping: a
+//! host with no SMTP route still exits 0, because `--dry-run` is what the
+//! README tells a reader to trust.
+
+use std::io::Write as _;
+use std::path::{Path, PathBuf};
+use std::process::Command;
+
+use crate::config::Config;
+
+/// How one check ended.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum Verdict {
+    /// Anything that needs it can go ahead.
+    Ok,
+    /// Worth knowing, not worth stopping for.
+    Warn,
+    /// Something spectral cannot work without.
+    Fail,
+    /// Not looked at, because something it depends on failed first.
+    Skipped,
+}
+
+impl Verdict {
+    fn label(self) -> &'static str {
+        match self {
+            Self::Ok => "ok",
+            Self::Warn => "warn",
+            Self::Fail => "fail",
+            Self::Skipped => "skip",
+        }
+    }
+
+    fn is_failure(self) -> bool {
+        matches!(self, Self::Fail)
+    }
+}
+
+/// One check and what it found.
+#[derive(Debug, Clone)]
+pub struct Check {
+    /// Short name, so the summary can name the one that failed.
+    pub name: &'static str,
+    pub verdict: Verdict,
+    pub detail: String,
+    /// What to do about it, printed under the line.
+    pub fix: Option<String>,
+}
+
+impl Check {
+    fn ok(name: &'static str, detail: impl Into<String>) -> Self {
+        Self {
+            name,
+            verdict: Verdict::Ok,
+            detail: detail.into(),
+            fix: None,
+        }
+    }
+
+    fn warn(name: &'static str, detail: impl Into<String>, fix: impl Into<String>) -> Self {
+        Self {
+            name,
+            verdict: Verdict::Warn,
+            detail: detail.into(),
+            fix: Some(fix.into()),
+        }
+    }
+
+    fn fail(name: &'static str, detail: impl Into<String>, fix: impl Into<String>) -> Self {
+        Self {
+            name,
+            verdict: Verdict::Fail,
+            detail: detail.into(),
+            fix: Some(fix.into()),
+        }
+    }
+
+    fn skipped(name: &'static str, detail: impl Into<String>) -> Self {
+        Self {
+            name,
+            verdict: Verdict::Skipped,
+            detail: detail.into(),
+            fix: None,
+        }
+    }
+}
+
+/// Everything the checks found.
+#[derive(Debug, Clone)]
+pub struct Report {
+    pub checks: Vec<Check>,
+}
+
+impl Report {
+    /// Whether anything hard failed. Warnings do not count.
+    #[must_use]
+    pub fn ok(&self) -> bool {
+        !self.checks.iter().any(|check| check.verdict.is_failure())
+    }
+
+    /// The first hard failure, which is the one worth naming.
+    #[must_use]
+    pub fn first_failure(&self) -> Option<&Check> {
+        self.checks.iter().find(|check| check.verdict.is_failure())
+    }
+
+    fn count(&self, verdict: Verdict) -> usize {
+        self.checks
+            .iter()
+            .filter(|check| check.verdict == verdict)
+            .count()
+    }
+
+    /// The report as `main` prints it: one line per check, the fix under it,
+    /// and a summary that names the first failure.
+    #[must_use]
+    pub fn render(&self) -> String {
+        let mut out = String::new();
+        for check in &self.checks {
+            out.push_str(&format!(
+                "{:<4} {:<23} {}\n",
+                check.verdict.label(),
+                check.name,
+                check.detail
+            ));
+            if let Some(fix) = &check.fix {
+                out.push_str(&format!("     {:<23} -> {fix}\n", ""));
+            }
+        }
+
+        let failures = self.count(Verdict::Fail);
+        let warnings = self.count(Verdict::Warn);
+        match self.first_failure() {
+            Some(first) => out.push_str(&format!(
+                "doctor: {failures} failed, {warnings} warned; first failure: {}\n",
+                first.name
+            )),
+            None if warnings > 0 => {
+                out.push_str(&format!("doctor: nothing failed, {warnings} warned\n"));
+            }
+            None => out.push_str("doctor: everything checked out\n"),
+        }
+
+        out
+    }
+}
+
+/// Run every check, in the order a first attempt hits them.
+#[must_use]
+pub fn run(config: &Config) -> Report {
+    let tree = config.require_kernel_tree().ok().map(Path::to_path_buf);
+    let checks = vec![
+        tree_path(config),
+        tree_shape(config),
+        tree_file(
+            tree.as_deref(),
+            "scripts/checkpatch.pl",
+            "checkpatch.pl",
+            "the only thing that decides kernel style",
+        ),
+        tree_file(
+            tree.as_deref(),
+            "scripts/get_maintainer.pl",
+            "get_maintainer.pl",
+            "the only thing that knows who to mail",
+        ),
+        tree_file(
+            tree.as_deref(),
+            "MAINTAINERS",
+            "MAINTAINERS",
+            "the maintainer map the script reads",
+        ),
+        git_runs(),
+        send_email_invocable(),
+        sender_identity(config, tree.as_deref()),
+        mail_route(tree.as_deref()),
+        qemu_on_path(),
+        patch_dir_writable(config),
+        config_file(config),
+    ];
+
+    Report { checks }
+}
+
+/// Whether a config file is there, and where it is.
+///
+/// A warning: everything works without one, and the paths in the report above
+/// say where the settings came from. The file is what `spectral init` writes,
+/// so a missing one is a pointer rather than a problem.
+fn config_file(config: &Config) -> Check {
+    let path = config.file_path();
+    if path.is_file() {
+        Check::ok("config file", path.display().to_string())
+    } else {
+        Check::warn(
+            "config file",
+            format!(
+                "no config file at {}; the paths above are defaults",
+                path.display()
+            ),
+            "run `spectral init --tree <path>` to write one",
+        )
+    }
+}
+
+/// Where spectral thinks the tree is, and where it got that from.
+fn tree_path(config: &Config) -> Check {
+    let path = config.kernel_tree();
+    if path.is_dir() {
+        Check::ok(
+            "kernel tree",
+            format!("{} ({})", path.display(), config.kernel_tree_origin()),
+        )
+    } else {
+        Check::fail(
+            "kernel tree",
+            format!("{} ({})", path.display(), config.kernel_tree_origin()),
+            "clone a tree there, or point the path at one you have",
+        )
+    }
+}
+
+/// Whether the path really is a kernel source tree.
+fn tree_shape(config: &Config) -> Check {
+    if !config.kernel_tree().exists() {
+        return Check::skipped(
+            "kernel tree shape",
+            "not looked at: there is nothing at that path",
+        );
+    }
+
+    match config.require_kernel_tree() {
+        Ok(_) => Check::ok("kernel tree shape", "scripts/checkpatch.pl is there"),
+        Err(error) => Check::fail(
+            "kernel tree shape",
+            error.to_string(),
+            "point the tree path at a kernel checkout",
+        ),
+    }
+}
+
+/// One file inside the tree.
+fn tree_file(tree: Option<&Path>, rel: &'static str, name: &'static str, why: &str) -> Check {
+    let Some(tree) = tree else {
+        return Check::skipped(name, "not looked at: there is no tree");
+    };
+    let path = tree.join(rel);
+
+    if path.is_file() {
+        Check::ok(name, format!("{rel} ({why})"))
+    } else {
+        Check::fail(
+            name,
+            format!("no {rel} in {}", tree.display()),
+            "use a full kernel checkout, not a build directory",
+        )
+    }
+}
+
+/// Whether git runs at all.
+fn git_runs() -> Check {
+    match Command::new("git").arg("--version").output() {
+        Ok(output) if output.status.success() => {
+            let version = String::from_utf8_lossy(&output.stdout).trim().to_owned();
+            Check::ok("git", version)
+        }
+        Ok(output) => Check::fail(
+            "git",
+            format!(
+                "`git --version` failed ({})",
+                crate::error::exit_code(&output.status)
+            ),
+            "fix git on this machine before spectral can do anything",
+        ),
+        Err(error) => Check::fail("git", format!("could not run git: {error}"), "install git"),
+    }
+}
+
+/// Whether `git send-email` is installed.
+///
+/// `--dump-aliases` is the cheapest call that proves the script runs: it reads
+/// the same config send-email would and needs no patch and no mail host.
+fn send_email_invocable() -> Check {
+    let output = Command::new("git")
+        .arg("send-email")
+        .arg("--dump-aliases")
+        .output();
+
+    match output {
+        Ok(output) if output.status.success() => Check::ok("git send-email", "runs"),
+        Ok(output) => Check::fail(
+            "git send-email",
+            format!(
+                "`git send-email --dump-aliases` failed ({}): {}",
+                crate::error::exit_code(&output.status),
+                String::from_utf8_lossy(&output.stderr).trim_end()
+            ),
+            "install git's send-email support (on Arch: git is not enough on its own)",
+        ),
+        Err(error) => Check::fail(
+            "git send-email",
+            format!("could not run git send-email: {error}"),
+            "install git",
+        ),
+    }
+}
+
+/// Who a patch is sent as.
+///
+/// A hard failure: `git send-email` refuses a patch with no sender, and finding
+/// that out at the end of the loop is the worst time.
+fn sender_identity(config: &Config, tree: Option<&Path>) -> Check {
+    if let Some(from) = config.send_email_from() {
+        return Check::ok("sender identity", format!("{from} (from the config file)"));
+    }
+    let Some(tree) = tree else {
+        return Check::skipped("sender identity", "not looked at: there is no tree");
+    };
+    let email = git_config(tree, "user.email");
+
+    match email {
+        Some(email) if !email.trim().is_empty() => Check::ok("sender identity", email),
+        _ => Check::fail(
+            "sender identity",
+            "git has no user.email in this tree",
+            "set `git config --global user.email [email protected]`, or an identity in the config file",
+        ),
+    }
+}
+
+/// Whether anything would carry mail out.
+///
+/// A warning, not a failure: this host has no `sendemail.*` config at all and
+/// still runs `git send-email --dry-run` to completion, which is the half of
+/// the loop spectral itself relies on.
+fn mail_route(tree: Option<&Path>) -> Check {
+    let Some(tree) = tree else {
+        return Check::skipped("mail route", "not looked at: there is no tree");
+    };
+    let configured = Command::new("git")
+        .arg("-C")
+        .arg(tree)
+        .args(["config", "--get-regexp", r"^sendemail\."])
+        .output();
+
+    match configured {
+        Ok(output) if !String::from_utf8_lossy(&output.stdout).trim().is_empty() => {
+            Check::ok("mail route", "sendemail.* is configured")
+        }
+        _ => Check::warn(
+            "mail route",
+            "no sendemail.* config: --dry-run works, a real send will not",
+            "configure `git send-email` before dropping --dry-run",
+        ),
+    }
+}
+
+/// Whether qemu is there to boot with.
+///
+/// A warning: `kernel test` cannot run without it, and nothing else cares.
+fn qemu_on_path() -> Check {
+    match Command::new("qemu-system-x86_64").arg("--version").output() {
+        Ok(output) if output.status.success() => {
+            let version = String::from_utf8_lossy(&output.stdout)
+                .lines()
+                .next()
+                .unwrap_or_default()
+                .trim()
+                .to_owned();
+            Check::ok("qemu", version)
+        }
+        _ => Check::warn(
+            "qemu",
+            "qemu-system-x86_64 is not on $PATH, so `kernel test` cannot boot anything",
+            "install qemu (qemu-system-x86 on Arch)",
+        ),
+    }
+}
+
+/// Whether patches can be written where spectral wants them.
+///
+/// This is the one check with a side effect: it makes the directory when it is
+/// missing, which is what the patch verbs would do anyway, and says which of
+/// the two happened.
+fn patch_dir_writable(config: &Config) -> Check {
+    let dir: PathBuf = config.patch_dir().to_path_buf();
+    let existed = dir.is_dir();
+    if let Err(error) = std::fs::create_dir_all(&dir) {
+        return Check::fail(
+            "patch directory",
+            format!("{} cannot be created: {error}", dir.display()),
+            "point the patch directory somewhere writable",
+        );
+    }
+
+    let probe = dir.join(format!(".spectral-doctor-{}", std::process::id()));
+    let wrote = std::fs::File::create(&probe).and_then(|mut file| file.write_all(b"probe\n"));
+    let _ = std::fs::remove_file(&probe);
+
+    let state = if existed { "exists" } else { "created" };
+    match wrote {
+        Ok(()) => Check::ok(
+            "patch directory",
+            format!("{} ({state}, {})", dir.display(), config.patch_dir_origin()),
+        ),
+        Err(error) => Check::fail(
+            "patch directory",
+            format!("{} is not writable: {error}", dir.display()),
+            "point the patch directory somewhere writable",
+        ),
+    }
+}
+
+/// One key out of git's configuration, or nothing when it is unset.
+fn git_config(tree: &Path, key: &str) -> Option<String> {
+    let output = Command::new("git")
+        .arg("-C")
+        .arg(tree)
+        .args(["config", key])
+        .output()
+        .ok()?;
+
+    if output.status.success() {
+        Some(
+            String::from_utf8_lossy(&output.stdout)
+                .trim_end()
+                .to_owned(),
+        )
+    } else {
+        None
+    }
+}

src/error.rs

@@ -10,10 +10,24 @@ use std::process::ExitStatus;
 pub type Result<T, E = Error> = std::result::Result<T, E>;
 
 /// How a failed process is described in [`Error::ExternalCommand`].
+///
+/// A process killed by a signal has no exit code, and the bare word "signal"
+/// throws away which one: a SIGTERM from a `timeout` and a SIGSEGV from the
+/// program under test are different answers to why it stopped.
 pub(crate) fn exit_code(status: &ExitStatus) -> String {
-    status
-        .code()
-        .map_or_else(|| "signal".to_owned(), |code| code.to_string())
+    if let Some(code) = status.code() {
+        return code.to_string();
+    }
+
+    #[cfg(unix)]
+    {
+        use std::os::unix::process::ExitStatusExt as _;
+        if let Some(signal) = status.signal() {
+            return format!("signal {signal}");
+        }
+    }
+
+    "a signal".to_owned()
 }
 
 #[derive(Debug, thiserror::Error)]
@@ -36,13 +50,21 @@ pub enum Error {
     },
 
     /// An external tool could not even be started.
-    #[error("could not run `{program}`")]
+    #[error("could not run `{program}`: {source}")]
     CommandSpawn {
         program: String,
         #[source]
         source: std::io::Error,
     },
 
+    /// A patch file the user named could not be read.
+    #[error("`{path}` could not be read: {source}")]
+    PatchUnreadable {
+        path: PathBuf,
+        #[source]
+        source: std::io::Error,
+    },
+
     /// A patch file the user named does not exist.
     #[error("no patch named `{name}` in `{dir}`")]
     PatchNotFound { name: String, dir: PathBuf },
@@ -57,7 +79,7 @@ pub enum Error {
 
     /// One patch file was asked to carry a whole set.
     #[error(
-        "`{base}..HEAD` holds {count} commits; one patch file cannot carry a set (patch series support is not built yet)"
+        "`{base}..HEAD` holds {count} commits; one file cannot carry a set, so write it as a series with `--range {base}..HEAD`"
     )]
     RangeHoldsSeveralCommits { base: String, count: usize },
 
@@ -75,11 +97,120 @@ pub enum Error {
     #[error("`{path}` already exists; delete it or pick another revision")]
     RerollWouldOverwrite { path: PathBuf },
 
+    /// Bugzilla answered, but with something that is not a bug list.
+    #[error("bugzilla answered with something that is not a bug list: {source}")]
+    BugzillaNotABugList {
+        #[source]
+        source: serde_json::Error,
+    },
+
+    /// Bugzilla answered with an empty set of open bugs.
+    #[error("bugzilla reports no open bugs at all; try again later")]
+    BugzillaEmpty,
+
+    /// `--filter` matched nothing, which is a dead end rather than a pick.
+    #[error("no open bug matched `{filter}`; drop --filter or try another word")]
+    NoQuestCandidates { filter: String },
+
+    /// The tree built, or was expected to have built, and holds no image.
+    #[error("no bootable image at `{path}`; build the tree first or drop --no-build")]
+    ImageMissing { path: PathBuf },
+
+    /// `make` ran and failed.
+    #[error("`make` failed (exit {code}); the tree did not build")]
+    BuildFailed { code: String },
+
+    /// The thread the build was moved onto did not come back.
+    #[error("the build stopped before it finished: {source}")]
+    BuildTask {
+        #[source]
+        source: tokio::task::JoinError,
+    },
+
+    /// `patch create` was given neither a name nor a range.
+    #[error("`patch create` wants a NAME, or --range for a series")]
+    CreateNeedsName,
+
+    /// `--range` was given something that is not a range.
+    #[error("`{range}` is not a range; `--range` wants `<base>..<head>`, e.g. HEAD~3..HEAD")]
+    RangeNotARange { range: String },
+
+    /// `--cover-letter` without a series to put it in.
+    #[error("`--cover-letter` belongs to a series; add `--range <base>..<head>`")]
+    CoverLetterNeedsSeries,
+
+    /// A blurb with nothing in it would leave the template subject behind.
+    #[error("the cover letter blurb is empty; give it a first line, which becomes the subject")]
+    CoverLetterBlurbEmpty,
+
+    /// format-patch wrote no cover letter where one was expected.
+    #[error("no cover letter was written into `{dir}`; a cover letter was asked for")]
+    CoverLetterMissing { dir: PathBuf },
+
+    /// A directory was used as a series but carries no sidecar.
+    #[error("`{path}` holds no series.toml; create the series with `patch create --range`")]
+    SeriesManifestMissing { path: PathBuf },
+
+    /// The sidecar is there and cannot be read.
+    #[error("`{path}` is not a readable series manifest: {source}")]
+    SeriesManifestUnreadable {
+        path: PathBuf,
+        #[source]
+        source: toml::de::Error,
+    },
+
+    /// The sidecar could not be written.
+    #[error("the series manifest could not be written: {source}")]
+    SeriesManifestUnwritable {
+        #[source]
+        source: toml::ser::Error,
+    },
+
+    /// A superseded revision would not go, so the directory holds two of them.
+    #[error(
+        "these files could not be removed: {names}; `submit` on the directory would send both revisions"
+    )]
+    StaleSeriesFiles { names: String },
+
+    /// A directory was handed to `submit` and holds no patches.
+    #[error("`{dir}` holds no `.patch` files")]
+    NoPatchesInDirectory { dir: PathBuf },
+
+    /// `git format-patch` was asked for a set and the range held nothing.
+    #[error("`{range}` holds no commits; a series needs at least one")]
+    RangeHoldsNoCommits { range: String },
+
+    /// The config file is there and is not readable as TOML.
+    #[error("`{path}` is not a readable config file: {source}")]
+    ConfigUnreadable {
+        path: PathBuf,
+        #[source]
+        source: toml::de::Error,
+    },
+
+    /// The config file could not be written.
+    #[error("the config file could not be written: {source}")]
+    ConfigUnwritable {
+        #[source]
+        source: toml::ser::Error,
+    },
+
+    /// A path in the config file would resolve against the working directory.
+    #[error(
+        "`{path}` in the config file is not an absolute path; ${variable} and the default are, so this one is refused"
+    )]
+    ConfigPathRelative {
+        variable: &'static str,
+        path: PathBuf,
+    },
+
+    /// The config already answers the question `init` was asked.
+    #[error("`{path}` already points somewhere else; pass --force to overwrite it")]
+    ConfigSaysSomethingElse { path: PathBuf },
+
     #[error(transparent)]
     Io(#[from] std::io::Error),
 
-    // Reached once `kernel quest` stops being a stub.
-    #[allow(dead_code)]
     #[error(transparent)]
     Http(#[from] reqwest::Error),
 }

src/git.rs

@@ -67,9 +67,7 @@ impl Git {
                 program: "git".to_owned(),
                 args: format!("apply {}", args.join(" ")),
                 code: exit_code(&output.status),
-                stderr: String::from_utf8_lossy(&output.stderr)
-                    .trim_end()
-                    .to_owned(),
+                stderr: told_off(&output),
             });
         }
 
@@ -149,12 +147,49 @@ impl Git {
         Ok(())
     }
 
-    /// Resolve a revision to a commit hash.
+    /// Resolve a revision, or `None` when there is no such revision.
     ///
-    /// Callers want the hash: a branch name can move under a command that is
-    /// about to build a range out of it.
-    pub fn rev_parse(&self, rev: &str) -> Result<String> {
-        self.run(&["rev-parse", "--verify", "--quiet", rev])
+    /// A revision that does not resolve and a repository that is not there are
+    /// both failures to git, and they are not the same answer: git says so on
+    /// stderr when the repository is missing, and `--quiet` keeps a missing
+    /// revision silent. Reading that difference is what keeps "not a git
+    /// repository" from being reported as "no revision `master`".
+    pub fn rev_parse_optional(&self, rev: &str) -> Result<Option<String>> {
+        let args = ["rev-parse", "--verify", "--quiet", rev];
+        let output = self.attempt(&args)?;
+        if output.status.success() {
+            return Ok(Some(
+                String::from_utf8_lossy(&output.stdout)
+                    .trim_end()
+                    .to_owned(),
+            ));
+        }
+        if output.stdout.is_empty() && output.stderr.is_empty() {
+            return Ok(None);
+        }
+
+        Err(Error::ExternalCommand {
+            program: "git".to_owned(),
+            args: args.join(" "),
+            code: exit_code(&output.status),
+            stderr: told_off(&output),
+        })
+    }
+
+    /// Run git and hand back what happened, failure included.
+    ///
+    /// The one caller is [`Git::rev_parse_optional`], which has to look at a
+    /// non-zero exit rather than turn it into an error immediately.
+    fn attempt(&self, args: &[&str]) -> Result<std::process::Output> {
+        Command::new("git")
+            .arg("-C")
+            .arg(&self.repo)
+            .args(args)
+            .output()
+            .map_err(|source| Error::CommandSpawn {
+                program: format!("git {}", args.join(" ")),
+                source,
+            })
     }
 
     fn output(&self, args: &[&str]) -> Result<std::process::Output> {
@@ -173,12 +208,26 @@ impl Git {
                 program: "git".to_owned(),
                 args: args.join(" "),
                 code: exit_code(&output.status),
-                stderr: String::from_utf8_lossy(&output.stderr)
-                    .trim_end()
-                    .to_owned(),
+                stderr: told_off(&output),
             });
         }
 
         Ok(output)
     }
 }
+
+/// What a failed git said, wherever it said it.
+///
+/// git puts some failures on stdout rather than stderr. `git commit` with
+/// nothing staged explains itself there, and a reader handed an empty message
+/// cannot tell what went wrong.
+fn told_off(output: &std::process::Output) -> String {
+    for stream in [&output.stderr, &output.stdout] {
+        let said = String::from_utf8_lossy(stream);
+        if !said.trim().is_empty() {
+            return said.trim_end().to_owned();
+        }
+    }
+
+    "nothing was captured".to_owned()
+}

src/kernel/qemu.rs

@@ -1,13 +1,26 @@
 //! `spectral kernel test`: build the tree, then boot it under qemu.
 
-#![allow(dead_code)] // nothing is reachable until `run` stops being a stub
-
 use std::path::{Path, PathBuf};
-use std::process::ExitStatus;
+use std::process::{Command, ExitStatus, Stdio};
+
+use tokio::io::{AsyncBufReadExt as _, BufReader};
+use tokio::process::Command as AsyncCommand;
 
 use crate::cli::TestArgs;
 use crate::config::Config;
-use crate::error::Result;
+use crate::error::{Error, Result, exit_code};
+
+/// Where an x86 kernel leaves the image qemu boots.
+const IMAGE: &str = "arch/x86/boot/bzImage";
+
+/// The console the kernel is told to use.
+///
+/// It is the one that comes back on a terminal, which is the difference
+/// between a boot hang someone can read and one they cannot.
+const CONSOLE: &str = "console=ttyS0";
+
+/// The emulator, by the name the README's prerequisites list.
+const QEMU: &str = "qemu-system-x86_64";
 
 /// One qemu run.
 #[derive(Debug, Clone)]
@@ -20,25 +33,219 @@ pub struct Boot {
     pub extra_args: Vec<String>,
 }
 
+/// What one `kernel test` did.
+///
+/// The status is carried rather than flattened into a `()`: a boot that failed
+/// must not print the same thing as one that succeeded.
+#[derive(Debug, Clone)]
+pub struct Outcome {
+    /// The image qemu was given.
+    pub image: PathBuf,
+    /// How qemu ended. A kernel that panics and stays running ends in a signal
+    /// rather than in an exit code, and that is worth reporting as itself.
+    pub status: ExitStatus,
+}
+
+impl Outcome {
+    /// Whether qemu ended well.
+    #[must_use]
+    pub fn succeeded(&self) -> bool {
+        self.status.success()
+    }
+}
+
 /// Build the tree and hand back the path to the bootable image.
+///
+/// `make` inherits the terminal, because a kernel build that says nothing for
+/// ten minutes is indistinguishable from one that has hung.
 pub fn build(kernel_tree: &Path) -> Result<PathBuf> {
-    todo!(
-        "make -j$(nproc) in {}, then locate arch/x86/boot/bzImage",
-        kernel_tree.display()
-    )
+    let jobs = std::thread::available_parallelism().map_or(1, std::num::NonZero::get);
+    let status = Command::new("make")
+        .arg(format!("-j{jobs}"))
+        .current_dir(kernel_tree)
+        .status()
+        .map_err(|source| Error::CommandSpawn {
+            program: "make".to_owned(),
+            source,
+        })?;
+
+    if !status.success() {
+        return Err(Error::BuildFailed {
+            code: exit_code(&status),
+        });
+    }
+
+    existing_image(kernel_tree)
+}
+
+/// The qemu arguments for one boot, without the emulator itself.
+///
+/// Split out so the shape of the command line is a pure function a test can
+/// assert on, which a spawned qemu is not.
+fn boot_args(boot: &Boot) -> Vec<String> {
+    let mut args = vec![
+        "-kernel".to_owned(),
+        boot.kernel.display().to_string(),
+        "-append".to_owned(),
+        CONSOLE.to_owned(),
+        "-nographic".to_owned(),
+    ];
+
+    if let Some(rootfs) = &boot.rootfs {
+        args.push("-initrd".to_owned());
+        args.push(rootfs.display().to_string());
+    }
+    args.extend(boot.extra_args.iter().cloned());
+
+    args
 }
 
 /// Boot an image and wait for qemu to exit.
+///
+/// The serial console is streamed line by line rather than buffered until qemu
+/// exits: a boot that hangs halfway is exactly the case where the output that
+/// arrived is the whole diagnosis.
 pub async fn boot(kernel_tree: &Path, boot: &Boot) -> Result<ExitStatus> {
-    // TODO: qemu-system-x86_64 -kernel {boot.kernel} -append "console=ttyS0" \
-    //       -nographic, with -initrd when `rootfs` is set and `extra_args` on
-    //       the end. Stream serial output instead of buffering it.
-    let _ = (kernel_tree, boot);
-    todo!("boot under qemu and stream the console")
+    let mut child = AsyncCommand::new(QEMU)
+        .current_dir(kernel_tree)
+        .args(boot_args(boot))
+        .stdin(Stdio::null())
+        .stdout(Stdio::piped())
+        .stderr(Stdio::piped())
+        // A qemu left behind by a failed run would hold the image and the
+        // terminal, so it goes when this does.
+        .kill_on_drop(true)
+        .spawn()
+        .map_err(|source| Error::CommandSpawn {
+            program: QEMU.to_owned(),
+            source,
+        })?;
+
+    let console = child
+        .stdout
+        .take()
+        .map(|pipe| tokio::spawn(drain(pipe, false)));
+    let complaints = child
+        .stderr
+        .take()
+        .map(|pipe| tokio::spawn(drain(pipe, true)));
+    let status = child.wait().await?;
+    if let Some(console) = console {
+        let _ = console.await;
+    }
+    if let Some(complaints) = complaints {
+        let _ = complaints.await;
+    }
+
+    Ok(status)
 }
 
 /// `spectral kernel test`: build unless told not to, then boot.
-pub async fn run(config: &Config, args: TestArgs) -> Result<()> {
-    let _ = (config, args);
-    todo!("build + boot")
+pub async fn run(config: &Config, args: TestArgs) -> Result<Outcome> {
+    let tree = config.require_kernel_tree()?.to_path_buf();
+    let image = if args.no_build {
+        existing_image(&tree)?
+    } else {
+        // A kernel build blocks for minutes, and blocking the async runtime
+        // for that long stalls everything else it is holding.
+        let building = tree.clone();
+        tokio::task::spawn_blocking(move || build(&building))
+            .await
+            .map_err(|source| Error::BuildTask { source })??
+    };
+
+    let planned = Boot {
+        kernel: image.clone(),
+        rootfs: args.rootfs,
+        extra_args: args.qemu_args,
+    };
+    let status = boot(&tree, &planned).await?;
+
+    Ok(Outcome { image, status })
+}
+
+/// The image a `--no-build` run was asked to boot.
+fn existing_image(kernel_tree: &Path) -> Result<PathBuf> {
+    let image = kernel_tree.join(IMAGE);
+
+    if image.is_file() {
+        Ok(image)
+    } else {
+        Err(Error::ImageMissing { path: image })
+    }
+}
+
+/// Copy one of qemu's pipes to this process's own, line by line.
+///
+/// A read that fails ends the stream with a note rather than silently: the
+/// last lines of a console are often the reason the run is being read at all.
+async fn drain<R>(pipe: R, to_stderr: bool)
+where
+    R: tokio::io::AsyncRead + Unpin,
+{
+    let mut lines = BufReader::new(pipe).lines();
+
+    loop {
+        match lines.next_line().await {
+            Ok(Some(line)) if to_stderr => eprintln!("{line}"),
+            Ok(Some(line)) => println!("{line}"),
+            Ok(None) => break,
+            Err(error) => {
+                eprintln!("spectral: qemu's console stopped early: {error}");
+                break;
+            }
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn boot(rootfs: Option<&str>, extra_args: &[&str]) -> Boot {
+        Boot {
+            kernel: PathBuf::from("/tree/arch/x86/boot/bzImage"),
+            rootfs: rootfs.map(PathBuf::from),
+            extra_args: extra_args.iter().map(|arg| (*arg).to_owned()).collect(),
+        }
+    }
+
+    #[test]
+    fn a_boot_names_the_image_and_the_serial_console() {
+        assert_eq!(
+            boot_args(&boot(None, &[])),
+            vec![
+                "-kernel",
+                "/tree/arch/x86/boot/bzImage",
+                "-append",
+                "console=ttyS0",
+                "-nographic",
+            ]
+        );
+    }
+
+    #[test]
+    fn a_rootfs_becomes_an_initrd_after_the_kernel() {
+        assert_eq!(
+            boot_args(&boot(Some("/img/initramfs.img"), &[])),
+            vec![
+                "-kernel",
+                "/tree/arch/x86/boot/bzImage",
+                "-append",
+                "console=ttyS0",
+                "-nographic",
+                "-initrd",
+                "/img/initramfs.img",
+            ]
+        );
+    }
+
+    #[test]
+    fn extra_arguments_go_on_the_end_verbatim() {
+        assert_eq!(
+            boot_args(&boot(None, &["-smp", "2", "-m", "1G"]))[5..],
+            ["-smp", "2", "-m", "1G"],
+            "the pass-through arguments are the caller's, in the order it gave them"
+        );
+    }
 }

src/kernel/quest.rs

@@ -2,14 +2,29 @@
 //!
 //! The source sits behind [`QuestSource`], so adding a local TODO file or a
 //! syzbot scraper later means one new impl and no change to the command.
-
-#![allow(dead_code)] // nothing is reachable until `run` stops being a stub
+//!
+//! The data comes from bugzilla.kernel.org's REST API rather than its HTML:
+//! `buglist.cgi` caps at 200 rows and would have to be paginated, and the CSV
+//! export needs a quote-aware parser for nothing JSON does not already give.
 
 use std::future::Future;
+use std::time::{Duration, SystemTime, UNIX_EPOCH};
+
+use serde::Deserialize;
 
 use crate::cli::QuestArgs;
 use crate::config::Config;
-use crate::error::Result;
+use crate::error::{Error, Result};
+
+/// The bug fields the REST call asks for, which are the ones an [`Issue`]
+/// needs. `limit=0` means everything rather than nothing.
+const INCLUDE_FIELDS: &str = "id,summary,product,component";
+
+/// How long bugzilla gets before the command gives up.
+///
+/// Without one, a route that drops packets rather than refusing the connection
+/// hangs the command with nothing on screen and no way out but Ctrl-C.
+const REQUEST_TIMEOUT: Duration = Duration::from_secs(30);
 
 /// One piece of work, normalised across whatever source it came from.
 #[derive(Debug, Clone)]
@@ -23,6 +38,31 @@ pub struct Issue {
     pub url: String,
 }
 
+impl Issue {
+    /// What `main` prints: the JSON form when `--json` asked for it, otherwise
+    /// the readable one.
+    #[must_use]
+    pub fn render(&self, json: bool) -> String {
+        if json {
+            let value = serde_json::json!({
+                "id": &self.id,
+                "title": &self.title,
+                "component": &self.component,
+                "url": &self.url,
+            });
+            if let Ok(rendered) = serde_json::to_string_pretty(&value) {
+                return rendered;
+            }
+        }
+
+        let component = self.component.as_deref().unwrap_or("unspecified");
+        format!(
+            "{} {}\ncomponent: {component}\n{}",
+            self.id, self.title, self.url
+        )
+    }
+}
+
 /// Anything spectral can pull open work from.
 ///
 /// Written as `impl Future` rather than a bare `async fn` so the `Send` bound
@@ -46,29 +86,311 @@ impl Default for Bugzilla {
     }
 }
 
+impl Bugzilla {
+    /// The REST call that returns every open bug and the four fields wanted.
+    fn open_bugs_url(&self) -> String {
+        format!(
+            "{}/rest/bug?status=NEW&limit=0&include_fields={INCLUDE_FIELDS}",
+            self.base_url.trim_end_matches('/')
+        )
+    }
+
+    /// Where a human reads the bug.
+    fn issue_url(&self, id: u64) -> String {
+        format!(
+            "{}/show_bug.cgi?id={id}",
+            self.base_url.trim_end_matches('/')
+        )
+    }
+}
+
 impl QuestSource for Bugzilla {
     async fn fetch_open(&self) -> Result<Vec<Issue>> {
-        // TODO: GET `{base_url}/buglist.cgi` with status=NEW/ASSIGNED/REOPENED,
-        // walk the paginated result tables, and pull id + summary + product out
-        // of each row with `scraper`.
-        let _ = &self.base_url;
-        todo!("scrape open bugs from bugzilla.kernel.org")
+        let body = reqwest::Client::builder()
+            .timeout(REQUEST_TIMEOUT)
+            .build()?
+            .get(self.open_bugs_url())
+            .send()
+            .await?
+            .text()
+            .await?;
+
+        parse_open_bugs(self, &body)
     }
 }
 
+/// What the REST call answered with, in the shape it answered with it.
+#[derive(Debug, Deserialize)]
+struct BugList {
+    bugs: Vec<Bug>,
+}
+
+/// One bug, with only the fields that were asked for.
+#[derive(Debug, Deserialize)]
+struct Bug {
+    id: u64,
+    summary: String,
+    product: Option<String>,
+    component: Option<String>,
+}
+
+/// Read a `/rest/bug` answer into issues.
+///
+/// Kept separate from the call so a recorded answer can be asserted against
+/// without a network: what a live bugzilla returns is not something a test can
+/// pin, but the shape is.
+fn parse_open_bugs(source: &Bugzilla, body: &str) -> Result<Vec<Issue>> {
+    let list: BugList =
+        serde_json::from_str(body).map_err(|error| Error::BugzillaNotABugList { source: error })?;
+
+    Ok(list
+        .bugs
+        .into_iter()
+        .map(|bug| {
+            // Read the shared fields before `summary` moves out of the bug.
+            let component = place(&bug);
+            let url = source.issue_url(bug.id);
+
+            Issue {
+                id: bug.id.to_string(),
+                title: bug.summary,
+                component,
+                url,
+            }
+        })
+        .collect())
+}
+
+/// Where a bug lives, as far as the API says: `product/component` when it
+/// names both, whichever one it names otherwise.
+fn place(bug: &Bug) -> Option<String> {
+    match (&bug.product, &bug.component) {
+        (Some(product), Some(component)) => Some(format!("{product}/{component}")),
+        (Some(only), None) | (None, Some(only)) => Some(only.clone()),
+        (None, None) => None,
+    }
+}
+
+/// Whether an issue answers to a `--filter` word.
+///
+/// The title or the component containing it is a match, case-insensitively:
+/// the words someone remembers from a bug are rarely the ones with the right
+/// capitalisation.
+fn matches(issue: &Issue, filter: &str) -> bool {
+    let needle = filter.to_lowercase();
+
+    issue.title.to_lowercase().contains(&needle)
+        || issue
+            .component
+            .as_ref()
+            .is_some_and(|component| component.to_lowercase().contains(&needle))
+}
+
 /// Fetch the open issues and pick one.
 ///
-/// TODO: apply `args.filter` to the title or component before picking, and
-/// print JSON when `args.json` is set.
-pub async fn run(config: &Config, args: QuestArgs) -> Result<Issue> {
-    let _ = (config, args);
-    todo!("pick one open bug at random")
+/// The config is deliberately not consulted: a quest is a question about
+/// bugzilla, not about a kernel tree, so this verb works before anything has
+/// been cloned.
+pub async fn run(_config: &Config, args: QuestArgs) -> Result<Issue> {
+    let source = Bugzilla::default();
+    let mut issues = source.fetch_open().await?;
+
+    if let Some(filter) = &args.filter {
+        issues.retain(|issue| matches(issue, filter));
+    }
+
+    let picked = pick_random(&issues, seed()).ok_or_else(|| match &args.filter {
+        Some(filter) => Error::NoQuestCandidates {
+            filter: filter.clone(),
+        },
+        None => Error::BugzillaEmpty,
+    })?;
+
+    Ok(picked.clone())
+}
+
+/// A seed that changes between runs, for a pick nobody can rerun by accident.
+///
+/// The low bits of the clock are the ones that move, and those are the ones a
+/// caller of [`pick_random`] folds through the xorshift.
+fn seed() -> u64 {
+    SystemTime::now()
+        .duration_since(UNIX_EPOCH)
+        .map_or(0, |elapsed| elapsed.as_nanos() as u64)
 }
 
 /// Choose one issue at random. `seed` keeps the pick reproducible in tests.
 pub fn pick_random(issues: &[Issue], seed: u64) -> Option<&Issue> {
-    todo!(
-        "index into {} candidate issues with seed {seed}",
-        issues.len()
-    )
+    if issues.is_empty() {
+        return None;
+    }
+
+    let index = (xorshift(seed) % issues.len() as u64) as usize;
+
+    issues.get(index)
+}
+
+/// One step of xorshift64, so a clock seed becomes a spread-out index without
+/// a `rand` dependency.
+fn xorshift(mut state: u64) -> u64 {
+    state ^= state << 13;
+    state ^= state >> 7;
+    state ^= state << 17;
+
+    state
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    /// A `/rest/bug` answer, recorded from the live API during planning and
+    /// trimmed to three bugs: one with both place fields, one with only a
+    /// component, and one with only a product.
+    const RECORDED: &str = r#"{
+        "bugs": [
+            {
+                "id": 219123,
+                "summary": "usb: xhci: device does not enumerate after resume",
+                "product": "Drivers",
+                "component": "USB"
+            },
+            {
+                "id": 218001,
+                "summary": "amdgpu: ring timeout on resume",
+                "component": "Video(AMDGPU/R600)"
+            },
+            {
+                "id": 215000,
+                "summary": "ppc64: build failure with gcc 15",
+                "product": "Platform Specific/Hardware"
+            }
+        ]
+    }"#;
+
+    fn issues() -> Vec<Issue> {
+        parse_open_bugs(&Bugzilla::default(), RECORDED).expect("the recorded answer parses")
+    }
+
+    #[test]
+    fn a_recorded_answer_becomes_issues() {
+        let issues = issues();
+
+        assert_eq!(issues.len(), 3);
+        assert_eq!(issues[0].id, "219123");
+        assert_eq!(
+            issues[0].title,
+            "usb: xhci: device does not enumerate after resume"
+        );
+        assert_eq!(
+            issues[0].url,
+            "https://bugzilla.kernel.org/show_bug.cgi?id=219123"
+        );
+    }
+
+    #[test]
+    fn a_bug_keeps_whichever_place_fields_it_has() {
+        let issues = issues();
+
+        assert_eq!(issues[0].component.as_deref(), Some("Drivers/USB"));
+        assert_eq!(
+            issues[1].component.as_deref(),
+            Some("Video(AMDGPU/R600)"),
+            "a component with no product is still worth showing"
+        );
+        assert_eq!(
+            issues[2].component.as_deref(),
+            Some("Platform Specific/Hardware")
+        );
+    }
+
+    #[test]
+    fn an_answer_that_is_not_a_bug_list_is_a_named_error() {
+        let error = parse_open_bugs(&Bugzilla::default(), "<html>nope</html>")
+            .expect_err("html is not JSON");
+
+        assert!(error.to_string().contains("is not a bug list"), "{error}");
+    }
+
+    #[test]
+    fn an_answer_with_no_bugs_parses_as_none() {
+        assert_eq!(
+            parse_open_bugs(&Bugzilla::default(), r#"{"bugs": []}"#)
+                .expect("an empty list")
+                .len(),
+            0
+        );
+    }
+
+    #[test]
+    fn a_filter_matches_the_title_or_the_component_whatever_the_case() {
+        let issues = issues();
+
+        assert!(matches(&issues[0], "xhci"));
+        assert!(matches(&issues[0], "XHCI"));
+        assert!(matches(&issues[1], "amdgpu"));
+        assert!(matches(&issues[2], "platform specific"));
+        assert!(!matches(&issues[0], "amdgpu"));
+    }
+
+    #[test]
+    fn the_same_seed_picks_the_same_issue() {
+        let issues = issues();
+
+        for seed in [0, 1, 7, 42, 12345, u64::MAX] {
+            let first = pick_random(&issues, seed).expect("a pick");
+            let again = pick_random(&issues, seed).expect("the same pick");
+
+            assert_eq!(first.id, again.id, "seed {seed} was not stable");
+        }
+    }
+
+    #[test]
+    fn there_is_nothing_to_pick_from_an_empty_list() {
+        assert!(pick_random(&[], 1).is_none());
+    }
+
+    #[test]
+    fn the_seed_spreads_across_the_list() {
+        // Not a distribution assertion: only that consecutive seeds do not all
+        // land on the same issue, which is what folding nothing would do, and that
+        // every pick is one of the candidates.
+        let issues = issues();
+        let picked: std::collections::HashSet<&str> = (0..64)
+            .filter_map(|seed| pick_random(&issues, seed).map(|issue| issue.id.as_str()))
+            .collect();
+
+        assert!(picked.len() > 1, "every seed picked the same issue");
+        assert!(
+            picked
+                .iter()
+                .all(|id| issues.iter().any(|issue| issue.id == *id))
+        );
+    }
+
+    #[test]
+    fn the_json_form_is_json_and_holds_every_field() {
+        let rendered = issues()[0].render(true);
+        let parsed: serde_json::Value =
+            serde_json::from_str(&rendered).expect("the JSON form parses");
+
+        assert_eq!(parsed["id"], "219123");
+        assert_eq!(parsed["component"], "Drivers/USB");
+        assert_eq!(
+            parsed["url"],
+            "https://bugzilla.kernel.org/show_bug.cgi?id=219123"
+        );
+        assert!(parsed["title"].as_str().is_some_and(|t| t.contains("xhci")));
+    }
+
+    #[test]
+    fn the_readable_form_names_the_component_and_the_url() {
+        let rendered = issues()[1].render(false);
+
+        assert!(
+            rendered.contains("component: Video(AMDGPU/R600)"),
+            "{rendered}"
+        );
+        assert!(rendered.contains("show_bug.cgi?id=218001"), "{rendered}");
+    }
 }

src/main.rs

@@ -6,6 +6,7 @@
 
 mod cli;
 mod config;
+mod doctor;
 mod error;
 mod git;
 mod kernel;
@@ -40,14 +41,27 @@ async fn run(cli: Cli) -> Result<ExitCode> {
     match cli.command {
         Command::Kernel { command } => match command {
             KernelCommand::Quest(args) => {
+                let json = args.json;
                 let issue = kernel::quest::run(&config, args).await?;
-                println!("{} {}", issue.id, issue.title);
-                println!("{}", issue.url);
+                println!("{}", issue.render(json));
                 Ok(ExitCode::SUCCESS)
             }
-            KernelCommand::Test(args) => kernel::qemu::run(&config, args)
-                .await
-                .map(|()| ExitCode::SUCCESS),
+            KernelCommand::Test(args) => {
+                let outcome = kernel::qemu::run(&config, args).await?;
+                println!("image: {}", outcome.image.display());
+                if outcome.succeeded() {
+                    println!("qemu exited cleanly");
+                    Ok(ExitCode::SUCCESS)
+                } else {
+                    // A boot that failed is not a crash of spectral, so this
+                    // reads as a result rather than as an error.
+                    println!(
+                        "qemu exited with status {}",
+                        crate::error::exit_code(&outcome.status)
+                    );
+                    Ok(ExitCode::FAILURE)
+                }
+            }
         },
 
         Command::Patch { command } => match command {
@@ -89,6 +103,27 @@ async fn run(cli: Cli) -> Result<ExitCode> {
                 Ok(ExitCode::SUCCESS)
             }
         },
+
+        Command::Doctor => {
+            let report = doctor::run(&config);
+            print!("{}", report.render());
+            Ok(if report.ok() {
+                ExitCode::SUCCESS
+            } else {
+                ExitCode::FAILURE
+            })
+        }
+
+        Command::Init(args) => {
+            let init = config::init(&args)?;
+            if init.wrote {
+                println!("wrote {}", init.config_file.display());
+            } else {
+                println!("{} already says this", init.config_file.display());
+            }
+            println!("tree: {}", init.kernel_tree.display());
+            Ok(ExitCode::SUCCESS)
+        }
     }
 }
 

src/patch/maintainers.rs

@@ -26,29 +26,42 @@ pub struct Recipients {
     pub touched: Vec<PathBuf>,
 }
 
-/// Look up recipients for a patch.
+/// The arguments one lookup runs with.
 ///
-/// One invocation over the patch. `--no-tree` because the script's own tree
-/// check wants a dozen marker files a working tree need not have, and
-/// `--pattern-depth=0` so a file matches every `F:` entry covering it rather
-/// than only the closest one.
-pub fn lookup(kernel_tree: &Path, patch: &Path) -> Result<Recipients> {
-    let patch_arg = patch.to_string_lossy().into_owned();
-    let output = run(
-        kernel_tree,
-        &[
+/// `--no-tree` because the script's own tree check wants a dozen marker files a
+/// working tree need not have, and `--pattern-depth=0` so a file matches every
+/// `F:` entry covering it rather than only the closest one.
+const LOOKUP_ARGS: [&str; 5] = [
     "--no-tree",
     "--git",
     "--roles",
     "--no-rolestats",
     "--pattern-depth=0",
-            &patch_arg,
-        ],
-    )?;
+];
+
+/// Look up recipients for a patch, or for every patch in a set.
+///
+/// One invocation over all the files: a series has one recipient list, and
+/// asking per patch would only repeat the same answer.
+pub fn lookup(kernel_tree: &Path, patches: &[PathBuf]) -> Result<Recipients> {
+    let mut args: Vec<String> = LOOKUP_ARGS.iter().map(|arg| (*arg).to_owned()).collect();
+    for patch in patches {
+        args.push(patch.to_string_lossy().into_owned());
+    }
+    let borrowed: Vec<&str> = args.iter().map(String::as_str).collect();
+    let output = run(kernel_tree, &borrowed)?;
 
     let entries: Vec<Entry> = output.lines().filter_map(parse_entry).collect();
+    let mut touched: Vec<PathBuf> = Vec::new();
+    for patch in patches {
+        for file in touched_files(patch)? {
+            if !touched.contains(&file) {
+                touched.push(file);
+            }
+        }
+    }
 
-    Ok(split(&entries, touched_files(patch)?))
+    Ok(split(&entries, touched))
 }
 
 /// Add extra addresses to the CC list, skipping ones already there.
@@ -164,9 +177,12 @@ fn parse_entry(line: &str) -> Option<Entry> {
 /// Paths git felt the need to quote are skipped rather than mangled. They are
 /// for reporting only; the lookup itself reads the patch.
 fn touched_files(patch: &Path) -> Result<Vec<PathBuf>> {
-    let patch = std::fs::read(patch)?;
+    let patch_bytes = std::fs::read(patch).map_err(|source| Error::PatchUnreadable {
+        path: patch.to_path_buf(),
+        source,
+    })?;
 
-    Ok(String::from_utf8_lossy(&patch)
+    Ok(String::from_utf8_lossy(&patch_bytes)
         .lines()
         .filter_map(|line| line.strip_prefix("diff --git "))
         .filter_map(|rest| rest.rsplit_once(" b/"))

src/patch/mod.rs

@@ -15,6 +15,7 @@
 
 pub mod checkpatch;
 pub mod maintainers;
+pub mod series;
 
 use std::path::{Path, PathBuf};
 
@@ -62,17 +63,20 @@ pub fn commit(config: &Config, args: CommitArgs) -> Result<()> {
 
 /// Write the change against `--base` out as a patch file.
 ///
-/// The name is normalised to end in `.patch` and the file lands in
-/// [`Config::patch_dir`] unless `--out` says otherwise. Returns the path
-/// written.
+/// One file, one commit: a range holding more than one commit is refused and
+/// pointed at `--range`, because a single file cannot carry a set.
 pub fn create(config: &Config, args: CreateArgs) -> Result<PathBuf> {
+    if args.cover_letter.is_some() && args.range.is_none() {
+        return Err(Error::CoverLetterNeedsSeries);
+    }
+    if let Some(range) = args.range.clone() {
+        return create_series(config, &args, &range);
+    }
+
+    let name = args.name.clone().ok_or(Error::CreateNeedsName)?;
     let tree = config.require_kernel_tree()?;
     let git = Git::new(tree);
-    let base = git
-        .rev_parse(&args.base)
-        .map_err(|_| Error::UnknownRevision {
-            rev: args.base.clone(),
-        })?;
+    let base = resolve_revision(&git, &args.base)?;
 
     // The patch is mail-formatted rather than a bare diff: `git send-email`
     // refuses the bare one with "No subject line".
@@ -90,12 +94,95 @@ pub fn create(config: &Config, args: CreateArgs) -> Result<PathBuf> {
 
     let dir = args.out.unwrap_or_else(|| config.patch_dir().to_path_buf());
     std::fs::create_dir_all(&dir)?;
-    let path = dir.join(patch_name(&args.name));
+    let path = dir.join(patch_name(&name));
     std::fs::write(&path, set)?;
 
     Ok(path)
 }
 
+/// Write a whole set, with a cover letter, into a directory of its own.
+///
+/// The directory carries a sidecar saying what was generated and at which
+/// revision, which is what lets `patch update` re-roll the set without the
+/// range being retyped.
+fn create_series(config: &Config, args: &CreateArgs, range: &str) -> Result<PathBuf> {
+    // Checked before anything is written: a blurb with no first line would
+    // otherwise leave generated files on disk with no sidecar beside them.
+    if let Some(blurb) = &args.cover_letter
+        && blurb.trim().is_empty()
+    {
+        return Err(Error::CoverLetterBlurbEmpty);
+    }
+
+    let tree = config.require_kernel_tree()?;
+    let git = Git::new(tree);
+    let resolved = resolve_range(&git, range)?;
+    let (base, head) = resolved.split_once("..").map_or_else(
+        || (resolved.clone(), resolved.clone()),
+        |(base, head)| (base.to_owned(), head.to_owned()),
+    );
+    let dir = series_dir(config, args);
+    std::fs::create_dir_all(&dir)?;
+
+    let files = series::generate(&git, &dir, &resolved, 1, args.cover_letter.as_deref())?;
+    series::Series {
+        base,
+        head,
+        version: 1,
+        files,
+        cover_letter: args.cover_letter.clone(),
+    }
+    .write(&dir)?;
+
+    Ok(dir)
+}
+
+/// The directory a series is written into.
+///
+/// `NAME` names a subdirectory of the patch directory, which keeps a set from
+/// mixing with the single patches beside it. Without a name the patch
+/// directory itself is the series directory.
+fn series_dir(config: &Config, args: &CreateArgs) -> PathBuf {
+    match (&args.out, &args.name) {
+        (Some(out), Some(name)) => out.join(name),
+        (Some(out), None) => out.clone(),
+        (None, Some(name)) => config.patch_dir().join(name),
+        (None, None) => config.patch_dir().to_path_buf(),
+    }
+}
+
+/// Turn `<base>..<head>` into hashes.
+///
+/// Both ends are resolved before format-patch runs: a branch that moves
+/// between resolving and generating would otherwise change which commits the
+/// set holds.
+fn resolve_range(git: &Git, range: &str) -> Result<String> {
+    let (base, head) = range
+        .split_once("..")
+        .ok_or_else(|| Error::RangeNotARange {
+            range: range.to_owned(),
+        })?;
+    let head = head.strip_prefix('.').unwrap_or(head);
+
+    let base = if base.is_empty() { "HEAD" } else { base };
+    let head = if head.is_empty() { "HEAD" } else { head };
+    let base_hash = resolve_revision(git, base)?;
+    let head_hash = resolve_revision(git, head)?;
+
+    Ok(format!("{base_hash}..{head_hash}"))
+}
+
+/// One end of a range, or the named error saying which revision was missing.
+///
+/// A tree that is not a git repository is reported as itself rather than as a
+/// missing revision: the two failures want different fixes.
+fn resolve_revision(git: &Git, rev: &str) -> Result<String> {
+    git.rev_parse_optional(rev)?
+        .ok_or_else(|| Error::UnknownRevision {
+            rev: rev.to_owned(),
+        })
+}
+
 /// What a `submit` run decided, so `main` can print it.
 #[derive(Debug, Clone)]
 pub struct Submission {
@@ -108,7 +195,7 @@ pub struct Submission {
     pub output: String,
 }
 
-/// Send a patch to whoever `get_maintainer.pl` names.
+/// Send a patch, or a whole series, to whoever `get_maintainer.pl` names.
 ///
 /// With `--dry-run` nothing leaves the machine: send-email prints the plan and
 /// nothing else happens. send-email's own refusals, a cover letter still
@@ -116,10 +203,13 @@ pub struct Submission {
 /// swallowed, because the exit code is what a script around this reads.
 pub fn submit(config: &Config, args: SubmitArgs) -> Result<Submission> {
     let tree = config.require_kernel_tree()?;
-    let patch = resolve_patch(config, &args.patch)?;
+    let patches = resolve_patches(config, &args.patches)?;
 
-    let mut recipients = maintainers::lookup(tree, &patch)?;
-    maintainers::add_cc(&mut recipients, &args.cc);
+    let mut recipients = maintainers::lookup(tree, &patches)?;
+    // `--cc` on the command line, then whatever the config file always copies.
+    let mut extras: Vec<String> = args.cc.clone();
+    extras.extend(config.always_cc().iter().cloned());
+    maintainers::add_cc(&mut recipients, &extras);
 
     let mut argv: Vec<String> = vec!["send-email".to_owned()];
     if args.dry_run {
@@ -128,6 +218,10 @@ pub fn submit(config: &Config, args: SubmitArgs) -> Result<Submission> {
         // an answer to send-email's confirmation question.
         argv.push("--confirm=never".to_owned());
     }
+    if let Some(from) = config.send_email_from() {
+        argv.push("--from".to_owned());
+        argv.push(from);
+    }
     for address in &recipients.to {
         argv.push("--to".to_owned());
         argv.push(address.clone());
@@ -140,7 +234,11 @@ pub fn submit(config: &Config, args: SubmitArgs) -> Result<Submission> {
         argv.push("--in-reply-to".to_owned());
         argv.push(message_id.clone());
     }
+    // A set goes out in one invocation, which is what threads the patches
+    // together and what send-email already knows how to do.
+    for patch in &patches {
         argv.push(patch.to_string_lossy().into_owned());
+    }
 
     let borrowed: Vec<&str> = argv.iter().map(String::as_str).collect();
     let git = Git::new(tree);
@@ -153,33 +251,93 @@ pub fn submit(config: &Config, args: SubmitArgs) -> Result<Submission> {
 
     Ok(Submission {
         recipients,
-        command: format!("git -C {} {}", tree.display(), shell_join(&argv)),
+        command: format!(
+            "git -C {} {}",
+            shell_quote(&tree.display().to_string()),
+            shell_join(&argv)
+        ),
         output,
     })
 }
 
-/// A command line a reader can paste, with the awkward arguments quoted.
+/// The patch files to send, in the order they will be sent.
+///
+/// A directory stands for a series: its sidecar decides the order when there
+/// is one, and otherwise the patch names sorted, which is the order
+/// format-patch numbered them in.
+fn resolve_patches(config: &Config, names: &[PathBuf]) -> Result<Vec<PathBuf>> {
+    let mut files: Vec<PathBuf> = Vec::new();
+
+    for name in names {
+        let resolved = resolve_patch(config, name)?;
+        if !resolved.is_dir() {
+            files.push(resolved);
+            continue;
+        }
+
+        let inside = match series::Series::read(&resolved) {
+            Ok(series) => series.paths(&resolved),
+            Err(Error::SeriesManifestMissing { .. }) => series::patches_in(&resolved)?
+                .into_iter()
+                .map(|name| resolved.join(name))
+                .collect(),
+            Err(other) => return Err(other),
+        };
+        if inside.is_empty() {
+            return Err(Error::NoPatchesInDirectory { dir: resolved });
+        }
+        files.extend(inside);
+    }
+
+    Ok(files)
+}
+
+/// A command line a reader can paste.
+///
+/// Quoting an argument only when it holds a space is not enough to make that
+/// true: `--in-reply-to <id@host>` is a redirection in bash, and an address
+/// with an apostrophe swallows the opening quote and arrives mangled. Anything
+/// outside a conservative safe set is single-quoted, and an apostrophe inside is
+/// escaped the way a shell reads it.
 fn shell_join(argv: &[String]) -> String {
     argv.iter()
-        .map(|arg| {
-            if arg.contains(' ') {
-                format!("'{arg}'")
-            } else {
-                arg.clone()
-            }
-        })
+        .map(|arg| shell_quote(arg))
         .collect::<Vec<_>>()
         .join(" ")
 }
 
-/// Re-roll a patch as `v<N>`.
+/// One argument, quoted if a shell would otherwise read something into it.
+fn shell_quote(arg: &str) -> String {
+    let plain = !arg.is_empty()
+        && arg.bytes().all(|byte| {
+            byte.is_ascii_alphanumeric()
+                || matches!(
+                    byte,
+                    b'/' | b'.' | b'-' | b'_' | b'+' | b':' | b'=' | b'@' | b','
+                )
+        });
+
+    if plain {
+        arg.to_owned()
+    } else {
+        format!("'{}'", arg.replace('\'', r"'\''"))
+    }
+}
+
+/// Re-roll a patch as `v<N>`, or a whole series when handed a directory.
 ///
-/// `000-kernel-patch.patch` becomes `v2-000-kernel-patch.patch`; an existing
-/// `vN-` prefix is replaced rather than stacked, so re-running it at the same
-/// revision is a no-op. `args.revision` overrides the inferred next number.
-/// Returns the path of the renamed file.
+/// A single patch is renamed: `000-kernel-patch.patch` becomes
+/// `v2-000-kernel-patch.patch`, and an existing `vN-` prefix is replaced
+/// rather than stacked, so re-running it at the same revision is a no-op.
+/// A directory is regenerated through `git format-patch --reroll-count`, so
+/// every file in it moves to the same revision. `args.revision` overrides the
+/// inferred next number. Returns the path of what moved.
 pub fn update(config: &Config, args: UpdateArgs) -> Result<PathBuf> {
     let patch = resolve_patch(config, &args.patch)?;
+    if patch.is_dir() {
+        return update_series(config, &patch, args.revision);
+    }
+
     let revision = match args.revision {
         Some(revision) => revision,
         None => current_revision(&patch) + 1,
@@ -198,6 +356,37 @@ pub fn update(config: &Config, args: UpdateArgs) -> Result<PathBuf> {
     Ok(renamed)
 }
 
+/// Re-roll every file in a series directory to `revision`.
+///
+/// The range comes out of the sidecar rather than being rebuilt as `base..HEAD`:
+/// a commit that landed on the branch after `create` is a different set, and
+/// picking it up silently would mail commits nobody asked to send. The
+/// superseded revision is removed only once the new one is entirely on disk, so
+/// a re-roll that fails halfway leaves the previous revision usable.
+fn update_series(config: &Config, dir: &Path, revision: Option<u32>) -> Result<PathBuf> {
+    let series = series::Series::read(dir)?;
+    let version = revision.unwrap_or(series.version + 1);
+    if version == series.version {
+        return Ok(dir.to_path_buf());
+    }
+
+    let tree = config.require_kernel_tree()?;
+    let git = Git::new(tree);
+    let range = format!("{}..{}", series.base, series.head);
+    let files = series::generate(&git, dir, &range, version, series.cover_letter.as_deref())?;
+    series::remove_superseded(dir, &series.files, &files)?;
+    series::Series {
+        base: series.base,
+        head: series.head,
+        version,
+        files,
+        cover_letter: series.cover_letter,
+    }
+    .write(dir)?;
+
+    Ok(dir.to_path_buf())
+}
+
 /// The path `patch` should have once it is revision `revision`.
 ///
 /// Kept separate from [`update`] because it is the rule worth having a test
@@ -229,11 +418,13 @@ fn strip_revision(name: &str) -> &str {
 
 /// Find the patch the user named.
 ///
-/// A path that is there is used as given. Anything else is looked for in the
-/// patch directory, which is what the README's examples assume: `patch submit
-/// 000-xhci-port-rearm.patch` from anywhere, without the path in front.
+/// A path that is there is used as given, a directory included: a series is a
+/// directory, and `submit` and `update` both take one. Anything else is looked
+/// for in the patch directory, which is what the README's examples assume:
+/// `patch submit 000-xhci-port-rearm.patch` from anywhere, without the path in
+/// front.
 fn resolve_patch(config: &Config, name: &Path) -> Result<PathBuf> {
-    if name.is_file() {
+    if name.is_file() || name.is_dir() {
         return Ok(name.to_path_buf());
     }
 
@@ -242,7 +433,7 @@ fn resolve_patch(config: &Config, name: &Path) -> Result<PathBuf> {
         |name| name.to_string_lossy().into_owned(),
     );
     let in_patch_dir = config.patch_dir().join(&file_name);
-    if in_patch_dir.is_file() {
+    if in_patch_dir.is_file() || in_patch_dir.is_dir() {
         return Ok(in_patch_dir);
     }
 

src/patch/series.rs

@@ -0,0 +1,222 @@
+//! Patch sets: what a series directory is, and the `git format-patch` calls
+//! that write one.
+//!
+//! The naming is not spectral's: `git format-patch` already numbers the files,
+//! prefixes a re-roll with `vN`, and writes the cover letter. What is spectral's
+//! is the sidecar that lets a re-roll know what it is re-rolling, and the
+//! refusal to leave two revisions in one directory.
+
+use std::path::{Path, PathBuf};
+
+use serde::{Deserialize, Serialize};
+
+use crate::error::{Error, Result};
+use crate::git::Git;
+
+/// The file a series directory carries.
+pub const MANIFEST: &str = "series.toml";
+
+/// The placeholder git leaves in a cover letter's subject line.
+const SUBJECT_TEMPLATE: &str = "*** SUBJECT HERE ***";
+
+/// The placeholder git leaves where the blurb belongs.
+const BLURB_TEMPLATE: &str = "*** BLURB HERE ***";
+
+/// What a series directory holds.
+///
+/// Minimal on purpose: the range, the revision, the files, and the cover letter
+/// blurb. Where sent patches are tracked afterwards is a later design question
+/// and is deliberately not answered here.
+#[derive(Debug, Clone, Serialize, Deserialize)]
+#[serde(deny_unknown_fields)]
+pub struct Series {
+    /// Commit the set was generated against, resolved to a hash so a branch
+    /// moving under a re-roll cannot change what the range means.
+    pub base: String,
+    /// The other end of that range, also a hash.
+    ///
+    /// Without it a re-roll would regenerate `base..HEAD`, which quietly picks
+    /// up every commit that landed on the branch since `create` and mails it
+    /// with the set.
+    pub head: String,
+    /// The revision every file in the directory is at.
+    pub version: u32,
+    /// The files, in the order they are sent: cover letter first.
+    pub files: Vec<String>,
+    /// The cover letter blurb, kept so a re-roll does not throw it away and
+    /// regenerate the template that `git send-email` refuses.
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub cover_letter: Option<String>,
+}
+
+impl Series {
+    /// Read the sidecar out of a series directory.
+    pub fn read(dir: &Path) -> Result<Self> {
+        let path = dir.join(MANIFEST);
+        let text = match std::fs::read_to_string(&path) {
+            Ok(text) => text,
+            // Only "there is no manifest here" means "this is not a series".
+            // Anything else is a real read failure and is reported as one.
+            Err(error) if error.kind() == std::io::ErrorKind::NotFound => {
+                return Err(Error::SeriesManifestMissing { path });
+            }
+            Err(error) => return Err(Error::Io(error)),
+        };
+
+        toml::from_str(&text).map_err(|source| Error::SeriesManifestUnreadable { path, source })
+    }
+
+    /// Write the sidecar into a series directory.
+    pub fn write(&self, dir: &Path) -> Result<()> {
+        let text =
+            toml::to_string(self).map_err(|source| Error::SeriesManifestUnwritable { source })?;
+        std::fs::write(dir.join(MANIFEST), text)?;
+
+        Ok(())
+    }
+
+    /// The patches this series holds, in the order they are sent.
+    #[must_use]
+    pub fn paths(&self, dir: &Path) -> Vec<PathBuf> {
+        self.files.iter().map(|name| dir.join(name)).collect()
+    }
+}
+
+/// Generate the set for `range` into `dir`, and return the file names written.
+///
+/// `version` above 1 goes through `--reroll-count`, which is what puts the same
+/// `vN-` prefix on every file including the cover letter. The names come from
+/// what format-patch says it wrote rather than from listing the directory: on a
+/// re-roll the directory still holds the revision being replaced, and a listing
+/// would read those back as part of the new set.
+pub fn generate(
+    git: &Git,
+    dir: &Path,
+    range: &str,
+    version: u32,
+    cover_letter: Option<&str>,
+) -> Result<Vec<String>> {
+    let mut args = vec!["format-patch".to_owned(), "--cover-letter".to_owned()];
+    if version > 1 {
+        args.push(format!("--reroll-count={version}"));
+    }
+    args.push("-o".to_owned());
+    args.push(dir.display().to_string());
+    args.push(range.to_owned());
+
+    let borrowed: Vec<&str> = args.iter().map(String::as_str).collect();
+    let written = git.run(&borrowed)?;
+    let files: Vec<String> = written
+        .lines()
+        .map(str::trim)
+        .filter(|line| !line.is_empty())
+        .map(|line| {
+            Path::new(line).file_name().map_or_else(
+                || line.to_owned(),
+                |name| name.to_string_lossy().into_owned(),
+            )
+        })
+        .collect();
+
+    if files.is_empty() {
+        return Err(Error::RangeHoldsNoCommits {
+            range: range.to_owned(),
+        });
+    }
+    if let Some(blurb) = cover_letter {
+        fill_cover_letter(dir, &files, blurb)?;
+    }
+
+    Ok(files)
+}
+
+/// Every patch in `dir`, cover letter first.
+///
+/// format-patch numbers the files, so their names sort into the order they are
+/// meant to be sent in.
+pub fn patches_in(dir: &Path) -> Result<Vec<String>> {
+    let entries = std::fs::read_dir(dir)?;
+    let mut names: Vec<String> = Vec::new();
+
+    for entry in entries {
+        let entry = entry?;
+        let name = entry.file_name().to_string_lossy().into_owned();
+        if name.ends_with(".patch") && entry.path().is_file() {
+            names.push(name);
+        }
+    }
+    names.sort();
+
+    Ok(names)
+}
+
+/// Put the blurb into a freshly generated cover letter.
+///
+/// git leaves `*** SUBJECT HERE ***` and `*** BLURB HERE ***` behind, and
+/// `git send-email` refuses to send a patch carrying either, so a series
+/// created without this stays unsendable on purpose: the refusal is louder than
+/// a cover letter nobody wrote.
+fn fill_cover_letter(dir: &Path, files: &[String], blurb: &str) -> Result<()> {
+    let Some(cover) = files.iter().find(|name| name.contains("cover-letter")) else {
+        return Err(Error::CoverLetterMissing {
+            dir: dir.to_path_buf(),
+        });
+    };
+    let path = dir.join(cover);
+    let original = std::fs::read_to_string(&path)?;
+    let subject = blurb.lines().next().unwrap_or_default().trim().to_owned();
+    if subject.is_empty() {
+        return Err(Error::CoverLetterBlurbEmpty);
+    }
+
+    let mut filled = String::with_capacity(original.len() + blurb.len());
+    for line in original.lines() {
+        match line
+            .strip_prefix("Subject: ")
+            .and_then(|subject| subject.rsplit_once(SUBJECT_TEMPLATE))
+        {
+            Some((head, _)) => {
+                filled.push_str("Subject: ");
+                filled.push_str(head);
+                filled.push_str(&subject);
+            }
+            None => filled.push_str(line),
+        }
+        filled.push('\n');
+    }
+
+    let filled = filled.replace(BLURB_TEMPLATE, blurb.trim_end());
+    std::fs::write(&path, filled)?;
+
+    Ok(())
+}
+
+/// Delete the files of the revision this one replaces.
+///
+/// Called only once every new file is on disk, so a failed re-roll cannot cost
+/// the previous revision. A file that is already gone is not a failure, because
+/// the directory is then in the state the re-roll wanted; a file that will not
+/// go is named rather than swallowed, since two revisions in one directory is
+/// what `submit` would send.
+pub fn remove_superseded(dir: &Path, old: &[String], new: &[String]) -> Result<()> {
+    let mut stuck: Vec<String> = Vec::new();
+
+    for name in old {
+        if new.contains(name) || name == MANIFEST {
+            continue;
+        }
+        if let Err(error) = std::fs::remove_file(dir.join(name))
+            && error.kind() != std::io::ErrorKind::NotFound
+        {
+            stuck.push(format!("{name} ({error})"));
+        }
+    }
+
+    if stuck.is_empty() {
+        Ok(())
+    } else {
+        Err(Error::StaleSeriesFiles {
+            names: stuck.join(", "),
+        })
+    }
+}

tests/cli_smoke.rs

@@ -29,6 +29,8 @@ fn every_verb_has_help_of_its_own() {
         &["patch", "create"],
         &["patch", "submit"],
         &["patch", "update"],
+        &["doctor"],
+        &["init"],
     ] {
         let mut args = verb.to_vec();
         args.push("--help");
@@ -67,16 +69,3 @@ fn a_leaf_missing_its_argument_exits_two() {
     let stderr = String::from_utf8_lossy(&output.stderr);
     assert!(stderr.contains("MESSAGE"), "{stderr}");
 }
-
-#[test]
-fn a_verb_that_is_still_a_stub_panics_where_it_says_it_does() {
-    // `kernel quest` is P5 and `kernel test` is P6. Until they land, this is
-    // the proof that the dispatch is wired end to end: exit 101 with the
-    // panic's own location in it.
-    let fixture = Fixture::kernel_tree();
-    let output = fixture.cli(&["kernel", "quest"]);
-
-    assert_eq!(output.status.code(), Some(101));
-    let stderr = String::from_utf8_lossy(&output.stderr);
-    assert!(stderr.contains("kernel/quest.rs"), "{stderr}");
-}

tests/common/mod.rs

@@ -161,6 +161,17 @@ impl Fixture {
         std::fs::set_permissions(&path, permissions).expect("make the script executable");
     }
 
+    /// Write an executable script into a directory of its own.
+    fn write_script_in(&self, dir: &Path, name: &str, body: &str) {
+        let path = dir.join(name);
+        std::fs::write(&path, body).expect("write the script");
+        let mut permissions = std::fs::metadata(&path)
+            .expect("stat the script")
+            .permissions();
+        permissions.set_mode(0o755);
+        std::fs::set_permissions(&path, permissions).expect("make the script executable");
+    }
+
     pub fn read(&self, rel: &str) -> String {
         std::fs::read_to_string(self.join(rel)).expect("read the file")
     }
@@ -214,6 +225,40 @@ impl Fixture {
         self.cli_env(args, &[])
     }
 
+    /// Run the built binary without `$SPECTRAL_KERNEL`, so the config file and
+    /// the built-in default are the only things left to resolve a tree from.
+    ///
+    /// `XDG_CONFIG_HOME` points into the fixture, which is where the test's
+    /// config file lives.
+    pub fn cli_without_the_tree_variable(&self, args: &[&str], env: &[(&str, &str)]) -> Output {
+        let mut command = Command::new(env!("CARGO_BIN_EXE_spectral"));
+        command
+            .args(args)
+            .current_dir(self.root.path())
+            .env_clear()
+            .env("PATH", std::env::var("PATH").unwrap_or_default())
+            .env("HOME", self.home.path())
+            .env("XDG_CONFIG_HOME", self.home.join("config"))
+            .env("GIT_CONFIG_GLOBAL", self.home.join("gitconfig"))
+            .env("GIT_CONFIG_SYSTEM", "/dev/null");
+
+        for (key, value) in env {
+            command.env(key, value);
+        }
+
+        command.output().expect("run spectral")
+    }
+
+    /// Write a config file into the fixture's own config directory.
+    pub fn write_config(&self, contents: &str) -> PathBuf {
+        let path = self.home.join("config/spectral/config.toml");
+        std::fs::create_dir_all(path.parent().expect("the config directory"))
+            .expect("create the config directory");
+        std::fs::write(&path, contents).expect("write the config file");
+
+        path
+    }
+
     /// Run the built binary with extra environment on top of the fixture's.
     pub fn cli_env(&self, args: &[&str], env: &[(&str, &str)]) -> Output {
         let mut command = Command::new(env!("CARGO_BIN_EXE_spectral"));
@@ -246,4 +291,52 @@ impl Fixture {
 
         command
     }
+
+    /// A `PATH` holding symlinks to exactly these programs, found on the
+    /// machine's own path.
+    ///
+    /// This is how a test takes a tool away: uninstalling qemu to prove the
+    /// missing-qemu path would be absurd, and pointing `PATH` somewhere narrow
+    /// asserts the same thing without touching the host.
+    pub fn restricted_path(&self, programs: &[&str]) -> PathBuf {
+        let bin = self.home.join("bin");
+        std::fs::create_dir_all(&bin).expect("create the restricted bin directory");
+
+        for program in programs {
+            let found = self.program(program);
+            std::os::unix::fs::symlink(found, bin.join(program)).expect("link the program");
+        }
+
+        bin
+    }
+
+    /// A `PATH` whose `git` is the machine's, except that `send-email` answers
+    /// with `answer` instead of running.
+    ///
+    /// The harness controls `PATH` and git's configuration but not git's own
+    /// exec-path, so whether the host has git's send-email support installed is
+    /// otherwise inherited from the machine. This makes the answer the test's,
+    /// in both directions.
+    pub fn path_with_send_email(&self, answer: u32) -> PathBuf {
+        let bin = self.home.join("gitbin");
+        std::fs::create_dir_all(&bin).expect("create the git bin directory");
+        let real = self.program("git");
+        let wrapper = format!(
+            "#!/bin/sh\nif [ \"$1\" = send-email ]; then exit {answer}; fi\nexec {} \"$@\"\n",
+            real.display()
+        );
+        self.write_script_in(&bin, "git", &wrapper);
+
+        bin
+    }
+
+    /// The machine's own copy of a program, found on its `PATH`.
+    fn program(&self, name: &str) -> PathBuf {
+        std::env::var("PATH")
+            .unwrap_or_default()
+            .split(':')
+            .map(|dir| Path::new(dir).join(name))
+            .find(|candidate| candidate.is_file())
+            .unwrap_or_else(|| panic!("{name} is not on this machine's PATH"))
+    }
 }

tests/config.rs

@@ -0,0 +1,373 @@
+//! The config file and `spectral init`, driven through the built binary.
+//!
+//! Precedence is asserted at the command line rather than in a unit test,
+//! because `std::env::set_var` is `unsafe` under edition 2024 and this crate
+//! allows no `unsafe`: the process under test is the one that sets the
+//! variables.
+
+mod common;
+
+use std::path::Path;
+
+use common::Fixture;
+
+fn stdout_of(output: &std::process::Output) -> String {
+    String::from_utf8_lossy(&output.stdout).into_owned()
+}
+
+fn stderr_of(output: &std::process::Output) -> String {
+    String::from_utf8_lossy(&output.stderr).into_owned()
+}
+
+/// A second kernel tree, so a test can tell two answers apart.
+fn other_tree(fixture: &Fixture) -> std::path::PathBuf {
+    let tree = fixture.join("other-tree");
+    std::fs::create_dir_all(tree.join("scripts")).expect("create the other tree");
+    std::fs::write(tree.join("scripts/checkpatch.pl"), "#!/bin/sh\n").expect("write checkpatch");
+    std::fs::write(tree.join("scripts/get_maintainer.pl"), "#!/bin/sh\n")
+        .expect("write the script");
+    std::fs::write(tree.join("MAINTAINERS"), "OTHER DRIVER\n").expect("write MAINTAINERS");
+
+    tree
+}
+
+#[test]
+fn a_config_file_supplies_the_tree_when_the_environment_does_not() {
+    let fixture = Fixture::kernel_tree();
+    fixture.write_config(&format!(
+        "kernel_tree = \"{}\"\npatch_dir = \"{}\"\n",
+        fixture.tree().display(),
+        fixture.home().join("patches").display()
+    ));
+
+    let output = fixture.cli_without_the_tree_variable(&["doctor"], &[]);
+
+    assert!(
+        output.status.success(),
+        "{}{}",
+        stdout_of(&output),
+        stderr_of(&output)
+    );
+    let stdout = stdout_of(&output);
+    assert!(stdout.contains("ok   kernel tree"), "{stdout}");
+    assert!(
+        stdout.contains("from the config file"),
+        "the report says the file answered: {stdout}"
+    );
+    assert!(
+        stdout.contains("ok   config file"),
+        "the file is a check of its own: {stdout}"
+    );
+}
+
+#[test]
+fn the_environment_beats_the_config_file() {
+    let fixture = Fixture::kernel_tree();
+    fixture.write_config(&format!(
+        "kernel_tree = \"{}\"\n",
+        other_tree(&fixture).display()
+    ));
+
+    let output = fixture.cli_without_the_tree_variable(
+        &["doctor"],
+        &[(
+            "SPECTRAL_KERNEL",
+            fixture.tree().to_str().expect("the tree"),
+        )],
+    );
+
+    assert!(output.status.success(), "{}", stdout_of(&output));
+    let stdout = stdout_of(&output);
+    assert!(stdout.contains("from $SPECTRAL_KERNEL"), "{stdout}");
+    assert!(
+        stdout.contains(fixture.tree().to_str().expect("the tree")),
+        "{stdout}"
+    );
+}
+
+#[test]
+fn the_file_beats_the_built_in_default() {
+    let fixture = Fixture::kernel_tree();
+    let other = other_tree(&fixture);
+    fixture.write_config(&format!("kernel_tree = \"{}\"\n", other.display()));
+
+    let output = fixture.cli_without_the_tree_variable(&["doctor"], &[]);
+
+    assert!(output.status.success(), "{}", stdout_of(&output));
+    let stdout = stdout_of(&output);
+    assert!(
+        stdout.contains(other.to_str().expect("the other tree")),
+        "the file's tree is the one doctor looked at: {stdout}"
+    );
+    assert!(
+        !stdout.contains(".spectral/linux"),
+        "the default was not used: {stdout}"
+    );
+}
+
+#[test]
+fn with_no_file_and_no_variable_the_default_is_used() {
+    let fixture = Fixture::kernel_tree();
+
+    let output = fixture.cli_without_the_tree_variable(&["doctor"], &[]);
+
+    assert_eq!(output.status.code(), Some(1));
+    let stdout = stdout_of(&output);
+    assert!(
+        stdout.contains(".spectral/linux"),
+        "the default is $HOME/.spectral/linux: {stdout}"
+    );
+    assert!(stdout.contains("the built-in default"), "{stdout}");
+}
+
+#[test]
+fn malformed_config_is_a_named_error_rather_than_a_panic() {
+    let fixture = Fixture::kernel_tree();
+    let path = fixture.write_config("kernel_tree = 42\n");
+
+    let output = fixture.cli_without_the_tree_variable(&["doctor"], &[]);
+
+    assert_eq!(
+        output.status.code(),
+        Some(1),
+        "a bad config is not a panic: {}{}",
+        stdout_of(&output),
+        stderr_of(&output)
+    );
+    let stderr = stderr_of(&output);
+    assert!(stderr.contains("is not a readable config file"), "{stderr}");
+    assert!(stderr.contains(&path.display().to_string()), "{stderr}");
+}
+
+#[test]
+fn an_unknown_key_is_refused_rather_than_ignored() {
+    let fixture = Fixture::kernel_tree();
+    fixture.write_config(&format!(
+        "kernel_tree = \"{}\"\ntree = \"a typo\"\n",
+        fixture.tree().display()
+    ));
+
+    let output = fixture.cli_without_the_tree_variable(&["doctor"], &[]);
+
+    assert_eq!(output.status.code(), Some(1));
+    assert!(
+        stderr_of(&output).contains("is not a readable config file"),
+        "{}",
+        stderr_of(&output)
+    );
+}
+
+#[test]
+fn a_relative_path_in_the_config_is_refused() {
+    let fixture = Fixture::kernel_tree();
+    fixture.write_config("kernel_tree = \"linux\"\n");
+
+    let output = fixture.cli_without_the_tree_variable(&["doctor"], &[]);
+
+    assert_eq!(output.status.code(), Some(1));
+    let stderr = stderr_of(&output);
+    assert!(stderr.contains("not an absolute path"), "{stderr}");
+}
+
+#[test]
+fn init_writes_the_config_and_a_second_run_changes_nothing() {
+    let fixture = Fixture::kernel_tree();
+
+    let first = fixture.cli_without_the_tree_variable(
+        &["init", "--tree", fixture.tree().to_str().expect("the tree")],
+        &[],
+    );
+    assert!(
+        first.status.success(),
+        "{}{}",
+        stdout_of(&first),
+        stderr_of(&first)
+    );
+    assert!(stdout_of(&first).contains("wrote"), "{}", stdout_of(&first));
+    let config = fixture.home().join("config/spectral/config.toml");
+    let written = std::fs::read(&config).expect("the config file");
+    assert!(
+        String::from_utf8_lossy(&written).contains(fixture.tree().to_str().expect("the tree")),
+        "{}",
+        String::from_utf8_lossy(&written)
+    );
+
+    let second = fixture.cli_without_the_tree_variable(
+        &["init", "--tree", fixture.tree().to_str().expect("the tree")],
+        &[],
+    );
+    assert!(second.status.success(), "{}", stderr_of(&second));
+    assert!(
+        stdout_of(&second).contains("already says this"),
+        "{}",
+        stdout_of(&second)
+    );
+    assert_eq!(
+        std::fs::read(&config).expect("the config file"),
+        written,
+        "the second run rewrote the file"
+    );
+}
+
+#[test]
+fn init_refuses_to_clobber_a_config_that_says_something_else() {
+    let fixture = Fixture::kernel_tree();
+    let other = other_tree(&fixture);
+    fixture.write_config(&format!("kernel_tree = \"{}\"\n", other.display()));
+
+    let refused = fixture.cli_without_the_tree_variable(
+        &["init", "--tree", fixture.tree().to_str().expect("the tree")],
+        &[],
+    );
+    assert_eq!(refused.status.code(), Some(1));
+    let stderr = stderr_of(&refused);
+    assert!(stderr.contains("already points somewhere else"), "{stderr}");
+    assert!(stderr.contains("--force"), "{stderr}");
+
+    let forced = fixture.cli_without_the_tree_variable(
+        &[
+            "init",
+            "--tree",
+            fixture.tree().to_str().expect("the tree"),
+            "--force",
+        ],
+        &[],
+    );
+    assert!(
+        forced.status.success(),
+        "{}{}",
+        stdout_of(&forced),
+        stderr_of(&forced)
+    );
+    let config = std::fs::read_to_string(fixture.home().join("config/spectral/config.toml"))
+        .expect("the config file");
+    assert!(
+        config.contains(fixture.tree().to_str().expect("the tree")),
+        "{config}"
+    );
+}
+
+#[test]
+fn init_verifies_the_tree_it_is_pointed_at() {
+    let fixture = Fixture::kernel_tree();
+    let not_a_tree = fixture.join("not-a-tree");
+    std::fs::create_dir_all(&not_a_tree).expect("create the directory");
+
+    let output = fixture.cli_without_the_tree_variable(
+        &[
+            "init",
+            "--tree",
+            not_a_tree.to_str().expect("the directory"),
+        ],
+        &[],
+    );
+
+    assert_eq!(output.status.code(), Some(1));
+    assert!(
+        stderr_of(&output).contains("not a kernel source tree"),
+        "{}",
+        stderr_of(&output)
+    );
+    assert!(
+        !Path::new(&fixture.home().join("config/spectral/config.toml")).exists(),
+        "a tree that did not verify must not be written into the config"
+    );
+}
+
+#[test]
+fn init_refuses_before_it_clones_anything() {
+    // The refusal is about the config file, so it has to happen before a
+    // multi-minute kernel clone rather than after one has already landed.
+    let fixture = Fixture::kernel_tree();
+    let other = other_tree(&fixture);
+    fixture.write_config(&format!("kernel_tree = \"{}\"\n", other.display()));
+    let into = fixture.home().join("should-not-exist");
+
+    let output = fixture.cli_without_the_tree_variable(
+        &[
+            "init",
+            "--clone",
+            fixture.tree().to_str().expect("the tree"),
+            "--tree",
+            into.to_str().expect("the destination"),
+        ],
+        &[],
+    );
+
+    assert_eq!(output.status.code(), Some(1));
+    assert!(
+        stderr_of(&output).contains("already points somewhere else"),
+        "{}",
+        stderr_of(&output)
+    );
+    assert!(
+        !into.exists(),
+        "the clone ran before the refusal was printed"
+    );
+}
+
+#[test]
+fn init_clones_a_tree_it_was_given_a_url_for() {
+    // A local path is a url git can clone, so this exercises the clone branch
+    // without a network.
+    let fixture = Fixture::kernel_tree();
+    let into = fixture.home().join("cloned");
+
+    let output = fixture.cli_without_the_tree_variable(
+        &[
+            "init",
+            "--clone",
+            fixture.tree().to_str().expect("the tree"),
+            "--tree",
+            into.to_str().expect("the destination"),
+        ],
+        &[],
+    );
+
+    assert!(
+        output.status.success(),
+        "{}{}",
+        stdout_of(&output),
+        stderr_of(&output)
+    );
+    assert!(into.join("scripts/checkpatch.pl").is_file());
+    assert!(into.join("MAINTAINERS").is_file());
+    let config = std::fs::read_to_string(fixture.home().join("config/spectral/config.toml"))
+        .expect("the config file");
+    assert!(config.contains("cloned"), "{config}");
+}
+
+#[test]
+fn the_config_file_carries_always_cc_and_an_identity_into_submit() {
+    let fixture = Fixture::kernel_tree();
+    fixture.work_on_a_branch();
+    fixture.write("drivers/foo/bar.c", common::EDITED);
+    fixture.commit_all("foo: return a + 1");
+    assert!(
+        fixture
+            .cli(&["patch", "create", "000-foo"])
+            .status
+            .success()
+    );
+    fixture.write_config(&format!(
+        "kernel_tree = \"{}\"\nalways_cc = [\"[email protected]\"]\n\n[send_email]\nfrom = \"Someone <[email protected]>\"\n",
+        fixture.tree().display()
+    ));
+
+    let output = fixture
+        .cli_without_the_tree_variable(&["patch", "submit", "000-foo.patch", "--dry-run"], &[]);
+
+    assert!(
+        output.status.success(),
+        "{}{}",
+        stdout_of(&output),
+        stderr_of(&output)
+    );
+    let stdout = stdout_of(&output);
+    assert!(stdout.contains("Cc: [email protected]"), "{stdout}");
+    assert!(
+        stdout.contains("--from 'Someone <[email protected]>'"),
+        "{stdout}"
+    );
+    assert!(stdout.contains("Dry-OK"), "{stdout}");
+}

tests/doctor.rs

@@ -0,0 +1,216 @@
+//! `spectral doctor`, driven through the built binary.
+//!
+//! The fixture controls `PATH` and git's configuration, so a missing qemu, a
+//! missing sender identity and a tree that is not a kernel tree are produced on
+//! purpose rather than inherited from whichever machine this runs on. That
+//! extends to git's own send-email support, which the harness cannot control
+//! through git's configuration: a `git` wrapper answers for it in both
+//! directions, so a host without it still passes.
+//!
+//! Every test name here carries the verb, so the plan's own command
+//! `cargo test --locked doctor` selects exactly this file's tests.
+
+mod common;
+
+use common::Fixture;
+
+fn stdout_of(output: &std::process::Output) -> String {
+    String::from_utf8_lossy(&output.stdout).into_owned()
+}
+
+fn stderr_of(output: &std::process::Output) -> String {
+    String::from_utf8_lossy(&output.stderr).into_owned()
+}
+
+/// Run `doctor` with a `git` that has send-email support, whatever the host has.
+fn doctor_with_send_email(fixture: &Fixture) -> std::process::Output {
+    let bin = fixture.path_with_send_email(0);
+
+    fixture.cli_env(
+        &["doctor"],
+        &[("PATH", bin.to_str().expect("the git bin directory"))],
+    )
+}
+
+#[test]
+fn doctor_passes_on_a_complete_fixture_tree() {
+    let fixture = Fixture::kernel_tree();
+
+    let output = doctor_with_send_email(&fixture);
+
+    assert!(
+        output.status.success(),
+        "{}{}",
+        stdout_of(&output),
+        stderr_of(&output)
+    );
+    let stdout = stdout_of(&output);
+    assert!(!stdout.contains("fail "), "{stdout}");
+    assert!(stdout.contains("ok   kernel tree"), "{stdout}");
+    assert!(
+        stdout.contains("from $SPECTRAL_KERNEL"),
+        "the report has to say which knob set the path: {stdout}"
+    );
+    assert!(stdout.contains("ok   git send-email"), "{stdout}");
+    assert!(
+        stdout.contains("nothing failed") || stdout.contains("everything checked out"),
+        "{stdout}"
+    );
+}
+
+#[test]
+fn doctor_names_the_first_hard_failure_when_the_tree_is_missing() {
+    let fixture = Fixture::bare();
+
+    let output = fixture.cli_env(&["doctor"], &[("SPECTRAL_KERNEL", "/nonexistent/linux")]);
+
+    assert_eq!(output.status.code(), Some(1));
+    let stdout = stdout_of(&output);
+    assert!(stdout.contains("fail kernel tree"), "{stdout}");
+    assert!(stdout.contains("first failure: kernel tree"), "{stdout}");
+    assert!(
+        stdout.contains("skip checkpatch.pl"),
+        "the checks that need a tree are not answers when there is none: {stdout}"
+    );
+    assert!(stdout.contains("-> "), "the fix hint is printed: {stdout}");
+}
+
+#[test]
+fn doctor_names_a_directory_that_is_not_a_kernel_tree() {
+    let fixture = Fixture::bare();
+    let tree = fixture.join("not-a-tree");
+    std::fs::create_dir_all(&tree).expect("create the directory");
+
+    let output = fixture.cli_env(
+        &["doctor"],
+        &[("SPECTRAL_KERNEL", tree.to_str().expect("the tree path"))],
+    );
+
+    assert_eq!(output.status.code(), Some(1));
+    let stdout = stdout_of(&output);
+    assert!(stdout.contains("fail kernel tree shape"), "{stdout}");
+    assert!(stdout.contains("not a kernel source tree"), "{stdout}");
+    assert!(
+        stdout.contains("first failure: kernel tree shape"),
+        "{stdout}"
+    );
+}
+
+#[test]
+fn doctor_warns_about_qemu_off_the_path_rather_than_failing() {
+    let fixture = Fixture::kernel_tree();
+    // A `PATH` holding the git wrapper and nothing else: qemu is gone, the
+    // rest is not.
+    let bin = fixture.path_with_send_email(0);
+
+    let output = fixture.cli_env(
+        &["doctor"],
+        &[("PATH", bin.to_str().expect("the git bin directory"))],
+    );
+
+    assert!(
+        output.status.success(),
+        "{}{}",
+        stdout_of(&output),
+        stderr_of(&output)
+    );
+    let stdout = stdout_of(&output);
+    assert!(stdout.contains("warn qemu"), "{stdout}");
+    assert!(
+        !stdout.contains("fail "),
+        "a missing qemu is not something the loop cannot work around: {stdout}"
+    );
+}
+
+#[test]
+fn doctor_fails_on_no_sender_identity_and_says_how_to_fix_it() {
+    let fixture = Fixture::kernel_tree();
+    // Both places git would find one: the tree's own config and the fixture's
+    // global one.
+    fixture.git(&["config", "--unset", "user.email"]);
+    std::fs::write(
+        fixture.home().join("gitconfig"),
+        "[core]\n\trepositoryformatversion = 0\n",
+    )
+    .expect("write a global config with no identity");
+
+    let output = doctor_with_send_email(&fixture);
+
+    assert_eq!(output.status.code(), Some(1));
+    let stdout = stdout_of(&output);
+    assert!(stdout.contains("fail sender identity"), "{stdout}");
+    assert!(
+        stdout.contains("user.email"),
+        "the failure says how to fix it: {stdout}"
+    );
+    assert!(
+        stdout.contains("first failure: sender identity"),
+        "{stdout}"
+    );
+}
+
+#[test]
+fn doctor_warns_when_git_has_no_send_email_support() {
+    // The direction the host cannot be trusted for: this machine has it, and a
+    // machine without it must fail the same way rather than pass by accident.
+    let fixture = Fixture::kernel_tree();
+    let bin = fixture.path_with_send_email(1);
+
+    let output = fixture.cli_env(
+        &["doctor"],
+        &[("PATH", bin.to_str().expect("the git bin directory"))],
+    );
+
+    assert_eq!(output.status.code(), Some(1));
+    let stdout = stdout_of(&output);
+    assert!(stdout.contains("fail git send-email"), "{stdout}");
+    assert!(stdout.contains("first failure: git send-email"), "{stdout}");
+}
+
+#[test]
+fn doctor_warns_about_no_mail_route_because_dry_runs_are_what_matter() {
+    // The fixture's git config has no sendemail.* at all, which is the state
+    // this machine's own config was in when --dry-run was verified.
+    let fixture = Fixture::kernel_tree();
+
+    let output = doctor_with_send_email(&fixture);
+
+    assert!(output.status.success());
+    let stdout = stdout_of(&output);
+    assert!(stdout.contains("warn mail route"), "{stdout}");
+    assert!(
+        stdout.contains("--dry-run works"),
+        "the warning says what still works: {stdout}"
+    );
+}
+
+#[test]
+fn doctor_reports_where_the_paths_came_from() {
+    let fixture = Fixture::kernel_tree();
+    let patches = fixture.home().join("patches");
+
+    let output = fixture.cli_env(
+        &["doctor"],
+        &[
+            (
+                "PATH",
+                fixture.path_with_send_email(0).to_str().expect("the bin"),
+            ),
+            (
+                "SPECTRAL_PATCH_DIR",
+                patches.to_str().expect("the patch dir"),
+            ),
+        ],
+    );
+
+    let stdout = stdout_of(&output);
+    assert!(stdout.contains("from $SPECTRAL_PATCH_DIR"), "{stdout}");
+    assert!(
+        stdout.contains(patches.to_str().expect("the patch dir")),
+        "{stdout}"
+    );
+    assert!(
+        patches.is_dir(),
+        "doctor is the one check with a side effect: it makes the directory it was pointed at"
+    );
+}

tests/patch_verbs.rs

@@ -152,6 +152,24 @@ fn a_bare_diff_is_refused_by_send_email() {
     assert!(stderr.contains("No subject line"), "{stderr}");
 }
 
+#[test]
+fn a_commit_with_nothing_staged_says_what_git_said() {
+    // git explains "nothing staged" on stdout, so an error path that only
+    // reads stderr prints a failure with nothing after it.
+    let fixture = Fixture::kernel_tree();
+    fixture.write("drivers/foo/bar.c", common::EDITED);
+
+    let output = fixture.cli(&["patch", "commit", "foo: nothing staged"]);
+
+    assert_eq!(output.status.code(), Some(1));
+    let stderr = String::from_utf8_lossy(&output.stderr);
+    assert!(stderr.contains("failed (exit 1)"), "{stderr}");
+    assert!(
+        stderr.contains("no changes added to commit") || stderr.contains("not staged"),
+        "git's own explanation was dropped: {stderr}"
+    );
+}
+
 #[test]
 fn create_names_a_base_that_does_not_resolve() {
     let fixture = Fixture::kernel_tree();
@@ -180,8 +198,8 @@ fn create_refuses_a_range_that_holds_more_than_one_commit() {
     let stderr = String::from_utf8_lossy(&output.stderr);
     assert!(stderr.contains("holds 2 commits"), "{stderr}");
     assert!(
-        stderr.contains("series support is not built yet"),
-        "{stderr}"
+        stderr.contains("--range"),
+        "the refusal has to say where a set belongs: {stderr}"
     );
 }
 
@@ -229,7 +247,7 @@ fn check_pipes_the_working_tree_diff_into_checkpatch_and_fails_on_errors() {
 }
 
 #[test]
-fn warnings_alone_do_not_fail_the_command() {
+fn checkpatch_warnings_alone_do_not_fail_the_command() {
     let fixture = Fixture::kernel_tree();
     fixture.write("drivers/foo/bar.c", common::EDITED);
 
@@ -246,7 +264,7 @@ fn warnings_alone_do_not_fail_the_command() {
 }
 
 #[test]
-fn a_run_with_no_total_line_counts_as_clean() {
+fn checkpatch_counts_a_run_with_no_total_line_as_clean() {
     // What a clean run looks like under checkpatch's own --terse, where the
     // summary line is suppressed entirely.
     let fixture = Fixture::kernel_tree();
@@ -524,12 +542,32 @@ fn submit_threads_a_reroll_off_the_patch_it_replaces() {
     assert!(output.status.success());
     let stdout = String::from_utf8_lossy(&output.stdout);
     assert!(
-        stdout.contains("--in-reply-to <[email protected]>"),
-        "{stdout}"
+        stdout.contains("--in-reply-to '<[email protected]>'"),
+        "an unquoted <...> is a redirection when pasted: {stdout}"
     );
     assert!(stdout.contains("In-Reply-To: <[email protected]>"), "{stdout}");
 }
 
+#[test]
+fn a_tree_that_is_not_a_repository_says_so_rather_than_blaming_a_revision() {
+    // `git rev-parse --verify --quiet master` fails both for a revision that is
+    // not there and for a directory that is not a repository. They want
+    // different fixes, so they get different messages.
+    let fixture = Fixture::bare();
+    fixture.write_script("scripts/checkpatch.pl", "#!/bin/sh\n");
+    fixture.write_script("scripts/get_maintainer.pl", "#!/bin/sh\n");
+
+    let output = fixture.cli(&["patch", "create", "000-foo"]);
+
+    assert_eq!(output.status.code(), Some(1));
+    let stderr = String::from_utf8_lossy(&output.stderr);
+    assert!(stderr.contains("not a git repository"), "{stderr}");
+    assert!(
+        !stderr.contains("no revision"),
+        "a missing repository is not a missing revision: {stderr}"
+    );
+}
+
 #[test]
 fn submit_refuses_a_template_cover_letter_instead_of_swallowing_it() {
     let fixture = Fixture::kernel_tree();

tests/qemu.rs

@@ -0,0 +1,135 @@
+//! `kernel test`, driven through the built binary against a fixture tree.
+//!
+//! Nothing here boots a kernel: qemu is taken off `PATH` deliberately, so the
+//! assertions are about the paths around the boot rather than about a machine
+//! that can run one. The real boot is the plan's P6 manual step.
+
+mod common;
+
+use common::Fixture;
+
+/// A fixture tree with something at the path qemu would be handed.
+fn fixture_with_image() -> Fixture {
+    let fixture = Fixture::kernel_tree();
+    fixture.write("arch/x86/boot/bzImage", "not really a kernel\n");
+    fixture.commit_all("fixture: add an image");
+
+    fixture
+}
+
+#[test]
+fn a_missing_qemu_is_named_rather_than_panicked_on() {
+    let fixture = fixture_with_image();
+    // A `PATH` with nothing on it: the binary itself is found by its full
+    // path, and qemu cannot be.
+    let bare = fixture.restricted_path(&[]);
+
+    let output = fixture.cli_env(
+        &["kernel", "test", "--no-build"],
+        &[("PATH", bare.to_str().expect("the restricted path"))],
+    );
+
+    assert_eq!(output.status.code(), Some(1));
+    let stderr = String::from_utf8_lossy(&output.stderr);
+    assert!(
+        stderr.contains("could not run `qemu-system-x86_64`"),
+        "{stderr}"
+    );
+    assert!(
+        !String::from_utf8_lossy(&output.stdout).contains("exited cleanly"),
+        "a boot that never started was reported as a success"
+    );
+}
+
+#[test]
+fn a_tree_with_no_image_is_named_rather_than_a_build_being_attempted() {
+    let fixture = Fixture::kernel_tree();
+
+    let output = fixture.cli(&["kernel", "test", "--no-build"]);
+
+    assert_eq!(output.status.code(), Some(1));
+    let stderr = String::from_utf8_lossy(&output.stderr);
+    assert!(stderr.contains("no bootable image at"), "{stderr}");
+    assert!(stderr.contains("arch/x86/boot/bzImage"), "{stderr}");
+}
+
+#[test]
+fn build_runs_make_in_the_tree_and_finds_the_image_it_wrote() {
+    // A Makefile that writes the image where a real build leaves it, and
+    // records that it ran. `sh` is the only tool it needs, so the restricted
+    // `PATH` can hold make and sh and still leave qemu out.
+    let fixture = Fixture::kernel_tree();
+    fixture.write("arch/x86/boot/.keep", "");
+    fixture.write(
+        "Makefile",
+        "all:\n\tprintf '' > arch/x86/boot/bzImage\n\tprintf 'built\\n' > .make-call\n",
+    );
+    fixture.commit_all("fixture: add a Makefile");
+    let bin = fixture.restricted_path(&["make", "sh"]);
+
+    let output = fixture.cli_env(
+        &["kernel", "test"],
+        &[("PATH", bin.to_str().expect("the restricted path"))],
+    );
+
+    assert_eq!(
+        fixture.read(".make-call"),
+        "built\n",
+        "make did not run in the tree"
+    );
+    // The image check passed, which is why the failure is qemu's rather than
+    // the image's.
+    assert_eq!(output.status.code(), Some(1));
+    let stderr = String::from_utf8_lossy(&output.stderr);
+    assert!(
+        stderr.contains("could not run `qemu-system-x86_64`"),
+        "the build did not get as far as qemu: {stderr}"
+    );
+}
+
+#[test]
+fn qemu_runs_with_the_arguments_the_plan_describes() {
+    // What qemu was handed, captured without needing a real qemu: the stub is
+    // reached through `PATH`, so the binary under test cannot tell.
+    let fixture = fixture_with_image();
+    fixture.write_script(
+        "bin/qemu-system-x86_64",
+        "#!/bin/sh\necho \"argv: $*\"\nexit 1\n",
+    );
+    let bin = fixture.join("bin");
+
+    let output = fixture.cli_env(
+        &[
+            "kernel",
+            "test",
+            "--no-build",
+            "--qemu-arg",
+            "-m",
+            "--qemu-arg",
+            "1G",
+        ],
+        &[("PATH", bin.to_str().expect("the stub bin directory"))],
+    );
+
+    assert_eq!(
+        output.status.code(),
+        Some(1),
+        "a failing qemu must not look clean: {}",
+        String::from_utf8_lossy(&output.stdout)
+    );
+    let stdout = String::from_utf8_lossy(&output.stdout);
+    assert!(
+        stdout.contains("-kernel ") && stdout.contains("arch/x86/boot/bzImage"),
+        "{stdout}"
+    );
+    assert!(
+        stdout.contains("-append console=ttyS0"),
+        "the console is what makes a boot readable: {stdout}"
+    );
+    assert!(stdout.contains("-nographic"), "{stdout}");
+    assert!(stdout.contains("-m 1G"), "the pass-through args: {stdout}");
+    assert!(
+        stdout.contains("qemu exited with status 1"),
+        "the exit status was flattened: {stdout}"
+    );
+}

tests/real_tools.rs

@@ -122,3 +122,48 @@ fn real_get_maintainer_fills_the_to_and_cc_lines() {
     );
     assert!(stdout.contains("Dry-OK"), "{stdout}");
 }
+
+#[test]
+#[ignore = "needs SPECTRAL_LIVE=1 and a network"]
+fn live_bugzilla_answers_with_one_issue() {
+    // The only test that talks to bugzilla.kernel.org. It asserts the shape of
+    // the answer rather than which bug came back, which is what a live API can
+    // be held to.
+    assert_eq!(
+        std::env::var("SPECTRAL_LIVE").as_deref(),
+        Ok("1"),
+        "run this with SPECTRAL_LIVE=1"
+    );
+    let fixture = Fixture::bare();
+    let output = fixture.cli(&["kernel", "quest", "--json"]);
+
+    assert!(
+        output.status.success(),
+        "{}",
+        String::from_utf8_lossy(&output.stderr)
+    );
+    let stdout = String::from_utf8_lossy(&output.stdout);
+    for field in ["\"id\"", "\"title\"", "\"component\"", "\"url\""] {
+        assert!(stdout.contains(field), "{field} is missing from {stdout}");
+    }
+    assert!(
+        stdout.contains("https://bugzilla.kernel.org/show_bug.cgi?id="),
+        "{stdout}"
+    );
+}
+
+#[test]
+#[ignore = "needs SPECTRAL_LIVE=1 and a network"]
+fn live_bugzilla_names_a_filter_that_matches_nothing() {
+    assert_eq!(
+        std::env::var("SPECTRAL_LIVE").as_deref(),
+        Ok("1"),
+        "run this with SPECTRAL_LIVE=1"
+    );
+    let fixture = Fixture::bare();
+    let output = fixture.cli(&["kernel", "quest", "--filter", "zzq-no-such-word-zzq"]);
+
+    assert_eq!(output.status.code(), Some(1));
+    let stderr = String::from_utf8_lossy(&output.stderr);
+    assert!(stderr.contains("no open bug matched"), "{stderr}");
+}

tests/series.rs

@@ -0,0 +1,464 @@
+//! Patch series, driven through the built binary against a fixture tree.
+//!
+//! Every test name here carries the verb, so the plan's own command
+//! `cargo test --locked series` selects exactly this file's tests.
+
+mod common;
+
+use std::path::{Path, PathBuf};
+
+use common::Fixture;
+
+/// The blurb the tests write into a cover letter.
+const BLURB: &str = "Port the re-arm to v2\n\nThis replaces the v1 series after review.";
+
+/// A tree with two commits on a branch of its own: the smallest thing that is
+/// really a set rather than a patch.
+fn fixture_with_two_commits() -> Fixture {
+    let fixture = Fixture::kernel_tree();
+    fixture.work_on_a_branch();
+    fixture.write("drivers/foo/bar.c", common::EDITED);
+    fixture.commit_all("foo: return a + 1");
+    fixture.write(
+        "drivers/foo/bar.c",
+        "static int foo(int a)\n{\n\treturn a + 2;\n}\n",
+    );
+    fixture.commit_all("foo: return a + 2");
+
+    fixture
+}
+
+/// The directory a series was written into, as `create` printed it.
+fn create_series(fixture: &Fixture, extra: &[&str]) -> PathBuf {
+    let mut args = vec!["patch", "create", "xhci-series", "--range", "master..HEAD"];
+    args.extend_from_slice(extra);
+    let output = fixture.cli(&args);
+
+    assert!(
+        output.status.success(),
+        "{}",
+        String::from_utf8_lossy(&output.stderr)
+    );
+
+    PathBuf::from(String::from_utf8_lossy(&output.stdout).trim())
+}
+
+/// What is in a directory, sorted, so two listings can be compared.
+fn listing(dir: &Path) -> Vec<String> {
+    let mut names: Vec<String> = std::fs::read_dir(dir)
+        .expect("read the series directory")
+        .map(|entry| {
+            entry
+                .expect("an entry")
+                .file_name()
+                .to_string_lossy()
+                .into_owned()
+        })
+        .collect();
+    names.sort();
+
+    names
+}
+
+/// The patches in a directory, in name order.
+fn patches(dir: &Path) -> Vec<String> {
+    listing(dir)
+        .into_iter()
+        .filter(|name| name.ends_with(".patch"))
+        .collect()
+}
+
+fn read(dir: &Path, name: &str) -> String {
+    std::fs::read_to_string(dir.join(name)).expect("read a file in the series directory")
+}
+
+#[test]
+fn a_series_gets_the_names_and_the_cover_letter_format_patch_gives_it() {
+    let fixture = fixture_with_two_commits();
+
+    let dir = create_series(&fixture, &["--cover-letter", BLURB]);
+
+    assert_eq!(
+        dir,
+        fixture.home().join(".spectral/patches/xhci-series"),
+        "the series belongs in a directory of its own"
+    );
+    let names = listing(&dir);
+    assert_eq!(names.len(), 4, "{names:?}");
+    assert_eq!(names[0], "0000-cover-letter.patch");
+    assert!(names[1].starts_with("0001-"), "{names:?}");
+    assert!(names[2].starts_with("0002-"), "{names:?}");
+    assert_eq!(names[3], "series.toml", "the sidecar says what this is");
+
+    // The sidecar records the whole range as hashes, the revision, and the
+    // files in the order they are sent. The range matters as much as the base:
+    // a re-roll rebuilt as `base..HEAD` would pick up later commits.
+    let manifest = read(&dir, "series.toml");
+    let master = fixture.git(&["rev-parse", "master"]);
+    let head = fixture.git(&["rev-parse", "HEAD"]);
+    assert!(
+        manifest.contains(&format!("base = \"{master}\"")),
+        "the base is a hash: {manifest}"
+    );
+    assert!(
+        manifest.contains(&format!("head = \"{head}\"")),
+        "the head is a hash too: {manifest}"
+    );
+    assert!(manifest.contains("version = 1"), "{manifest}");
+    assert!(manifest.contains("0000-cover-letter.patch"), "{manifest}");
+
+    // The blurb landed, and the template that send-email refuses is gone.
+    let cover = read(&dir, "0000-cover-letter.patch");
+    assert!(
+        cover.contains("Subject: [PATCH 0/2] Port the re-arm to v2"),
+        "{cover}"
+    );
+    assert!(cover.contains("This replaces the v1 series"), "{cover}");
+    assert!(!cover.contains("*** BLURB HERE ***"), "{cover}");
+    assert!(!cover.contains("*** SUBJECT HERE ***"), "{cover}");
+}
+
+#[test]
+fn a_series_goes_out_in_one_send_email_invocation() {
+    let fixture = fixture_with_two_commits();
+    create_series(&fixture, &["--cover-letter", BLURB]);
+
+    let output = fixture.cli(&["patch", "submit", "xhci-series", "--dry-run"]);
+
+    assert!(
+        output.status.success(),
+        "{}",
+        String::from_utf8_lossy(&output.stderr)
+    );
+    let stdout = String::from_utf8_lossy(&output.stdout);
+    let command = stdout
+        .lines()
+        .find(|line| line.contains("send-email --dry-run"))
+        .unwrap_or_else(|| panic!("no command line in {stdout}"));
+
+    for name in ["0000-cover-letter.patch", "0001-", "0002-"] {
+        assert!(command.contains(name), "{name} is not in {command}");
+    }
+    let cover_at = command.find("0000-cover-letter").expect("the cover letter");
+    let first_at = command.find("0001-").expect("the first patch");
+    assert!(
+        cover_at < first_at,
+        "the cover letter is sent first: {command}"
+    );
+    assert!(stdout.contains("Dry-OK"), "{stdout}");
+
+    // One lookup over the whole set: a series has one recipient list.
+    let call = fixture.read(".getmaintainer-call");
+    assert_eq!(
+        call.matches("argv:").count(),
+        1,
+        "the lookup ran more than once: {call}"
+    );
+    assert!(call.contains("0000-cover-letter.patch"), "{call}");
+    assert!(call.contains("0001-"), "{call}");
+}
+
+#[test]
+fn a_series_without_a_blurb_is_refused_by_send_email() {
+    // No --cover-letter, so format-patch's template subject is still in the
+    // file and send-email refuses the set. The refusal has to reach the user.
+    let fixture = fixture_with_two_commits();
+    create_series(&fixture, &[]);
+
+    let output = fixture.cli(&["patch", "submit", "xhci-series", "--dry-run"]);
+
+    assert_eq!(output.status.code(), Some(1));
+    let stderr = String::from_utf8_lossy(&output.stderr);
+    assert!(stderr.contains("Refusing to send"), "{stderr}");
+    assert!(stderr.contains("exit 25"), "{stderr}");
+}
+
+#[test]
+fn series_reroll_moves_every_file_at_once_and_stays_idempotent() {
+    let fixture = fixture_with_two_commits();
+    let dir = create_series(&fixture, &["--cover-letter", BLURB]);
+    let before = listing(&dir);
+
+    // No -v: the next revision is inferred from the sidecar.
+    let output = fixture.cli(&["patch", "update", "xhci-series"]);
+    assert!(
+        output.status.success(),
+        "{}",
+        String::from_utf8_lossy(&output.stderr)
+    );
+    assert_eq!(
+        String::from_utf8_lossy(&output.stdout).trim(),
+        dir.display().to_string()
+    );
+
+    let after = listing(&dir);
+    assert_eq!(
+        after.len(),
+        before.len(),
+        "the old revision was left beside the new one: {after:?}"
+    );
+    assert!(
+        patches(&dir).iter().all(|name| name.starts_with("v2-")),
+        "every patch moves together: {after:?}"
+    );
+    assert!(
+        after
+            .iter()
+            .any(|name| name == "v2-0000-cover-letter.patch")
+    );
+    assert!(read(&dir, "series.toml").contains("version = 2"));
+    assert!(
+        read(&dir, "v2-0000-cover-letter.patch").contains("This replaces the v1 series"),
+        "a re-roll threw the blurb away"
+    );
+
+    // The same revision again is a no-op, which is what keeps a double run
+    // from producing a v3.
+    let again = fixture.cli(&["patch", "update", "xhci-series", "-v", "2"]);
+    assert!(again.status.success());
+    assert_eq!(
+        String::from_utf8_lossy(&again.stdout).trim(),
+        dir.display().to_string()
+    );
+    let unchanged = listing(&dir);
+    assert_eq!(unchanged, after, "a second run at v2 changed the directory");
+    assert!(
+        !unchanged.iter().any(|name| name.starts_with("v3-")),
+        "{unchanged:?}"
+    );
+
+    // And the re-rolled set still sends, with the cover letter first.
+    let sent = fixture.cli(&["patch", "submit", "xhci-series", "--dry-run"]);
+    assert!(
+        sent.status.success(),
+        "{}",
+        String::from_utf8_lossy(&sent.stderr)
+    );
+    assert!(String::from_utf8_lossy(&sent.stdout).contains("Dry-OK"));
+}
+
+#[test]
+fn a_rerolled_series_holds_exactly_one_revision() {
+    let fixture = fixture_with_two_commits();
+    let dir = create_series(&fixture, &["--cover-letter", BLURB]);
+
+    // Straight to v3, so the files that must go are the unversioned ones.
+    assert!(
+        fixture
+            .cli(&["patch", "update", "xhci-series", "-v", "3"])
+            .status
+            .success()
+    );
+    assert!(
+        fixture
+            .cli(&["patch", "update", "xhci-series", "-v", "4"])
+            .status
+            .success()
+    );
+
+    let names = patches(&dir);
+    assert_eq!(names.len(), 3, "{names:?}");
+    assert!(
+        names.iter().all(|name| name.starts_with("v4-")),
+        "{names:?}"
+    );
+}
+
+#[test]
+fn series_reroll_does_not_pick_up_a_commit_that_landed_after_create() {
+    // The range a series was created for is the range it re-rolls. Rebuilding
+    // it as `base..HEAD` would quietly mail commits nobody asked to send.
+    let fixture = fixture_with_two_commits();
+    let dir = create_series(&fixture, &["--cover-letter", BLURB]);
+    assert_eq!(patches(&dir).len(), 3);
+
+    fixture.write(
+        "drivers/foo/bar.c",
+        "static int foo(int a)\n{\n\treturn a + 3;\n}\n",
+    );
+    fixture.commit_all("foo: return a + 3");
+
+    let output = fixture.cli(&["patch", "update", "xhci-series"]);
+    assert!(
+        output.status.success(),
+        "{}",
+        String::from_utf8_lossy(&output.stderr)
+    );
+
+    let names = patches(&dir);
+    assert_eq!(
+        names.len(),
+        3,
+        "a commit that landed after create joined the set: {names:?}"
+    );
+    assert!(
+        !names.iter().any(|name| name.contains("return-a-3")),
+        "{names:?}"
+    );
+    assert_eq!(
+        read(&dir, "series.toml").matches("version = 2").count(),
+        1,
+        "{}",
+        read(&dir, "series.toml")
+    );
+}
+
+#[test]
+fn series_reroll_tolerates_a_patch_that_is_already_gone() {
+    // A missing file is the state the re-roll wanted, not a failure it should
+    // report forever while leaving the sidecar describing a revision that is
+    // no longer on disk.
+    let fixture = fixture_with_two_commits();
+    let dir = create_series(&fixture, &["--cover-letter", BLURB]);
+    let doomed = patches(&dir)
+        .into_iter()
+        .find(|name| name.starts_with("0002-"))
+        .expect("the second patch");
+    std::fs::remove_file(dir.join(&doomed)).expect("remove a patch by hand");
+
+    let output = fixture.cli(&["patch", "update", "xhci-series"]);
+
+    assert!(
+        output.status.success(),
+        "a stale name stopped the re-roll: {}",
+        String::from_utf8_lossy(&output.stderr)
+    );
+    let names = patches(&dir);
+    assert_eq!(names.len(), 3, "{names:?}");
+    assert!(
+        names.iter().all(|name| name.starts_with("v2-")),
+        "{names:?}"
+    );
+    assert!(read(&dir, "series.toml").contains("version = 2"));
+
+    // And it is ready to send, which is the thing the old failure made
+    // impossible: the sidecar and the directory agree again.
+    let sent = fixture.cli(&["patch", "submit", "xhci-series", "--dry-run"]);
+    assert!(
+        sent.status.success(),
+        "{}",
+        String::from_utf8_lossy(&sent.stderr)
+    );
+}
+
+#[test]
+fn series_create_refuses_an_empty_blurb_before_it_writes_anything() {
+    let fixture = fixture_with_two_commits();
+
+    let output = fixture.cli(&[
+        "patch",
+        "create",
+        "xhci-series",
+        "--range",
+        "master..HEAD",
+        "--cover-letter",
+        "   ",
+    ]);
+
+    assert_eq!(output.status.code(), Some(1));
+    assert!(
+        String::from_utf8_lossy(&output.stderr).contains("blurb is empty"),
+        "{}",
+        String::from_utf8_lossy(&output.stderr)
+    );
+    let dir = fixture.home().join(".spectral/patches/xhci-series");
+    assert!(
+        !dir.exists(),
+        "files with no sidecar beside them were left behind: {:?}",
+        listing(&dir)
+    );
+}
+
+#[test]
+fn a_directory_that_is_not_a_series_still_sends_its_patches() {
+    // No sidecar: the directory is read as a pile of patches, in name order,
+    // which is the order format-patch numbered them in.
+    let fixture = fixture_with_two_commits();
+    let dir = fixture.home().join("hand-made");
+    std::fs::create_dir_all(&dir).expect("create the directory");
+    fixture.git(&[
+        "format-patch",
+        "-o",
+        dir.to_str().expect("the directory path"),
+        "master..HEAD",
+    ]);
+
+    let output = fixture.cli(&[
+        "patch",
+        "submit",
+        dir.to_str().expect("the directory path"),
+        "--dry-run",
+    ]);
+
+    assert!(
+        output.status.success(),
+        "{}",
+        String::from_utf8_lossy(&output.stderr)
+    );
+    let stdout = String::from_utf8_lossy(&output.stdout);
+    assert!(
+        stdout.contains("0001-") && stdout.contains("0002-"),
+        "{stdout}"
+    );
+}
+
+#[test]
+fn a_series_wants_a_range_and_a_range_that_is_not_one_is_named() {
+    let fixture = fixture_with_two_commits();
+
+    let not_a_range = fixture.cli(&["patch", "create", "x", "--range", "master"]);
+    assert_eq!(not_a_range.status.code(), Some(1));
+    let stderr = String::from_utf8_lossy(&not_a_range.stderr);
+    assert!(stderr.contains("is not a range"), "{stderr}");
+
+    let orphan_blurb = fixture.cli(&["patch", "create", "x", "--cover-letter", "hi"]);
+    assert_eq!(orphan_blurb.status.code(), Some(1));
+    assert!(
+        String::from_utf8_lossy(&orphan_blurb.stderr).contains("belongs to a series"),
+        "{}",
+        String::from_utf8_lossy(&orphan_blurb.stderr)
+    );
+}
+
+#[test]
+fn create_needs_a_name_when_no_series_range_is_given() {
+    let fixture = fixture_with_two_commits();
+
+    let output = fixture.cli(&["patch", "create"]);
+
+    assert_eq!(output.status.code(), Some(1));
+    assert!(
+        String::from_utf8_lossy(&output.stderr).contains("wants a NAME"),
+        "{}",
+        String::from_utf8_lossy(&output.stderr)
+    );
+}
+
+#[test]
+fn a_series_with_no_name_lands_in_the_patch_directory_itself() {
+    // NAME names the series directory, so leaving it off means the patch
+    // directory is the series directory.
+    let fixture = fixture_with_two_commits();
+
+    let output = fixture.cli(&[
+        "patch",
+        "create",
+        "--range",
+        "master..HEAD",
+        "--cover-letter",
+        BLURB,
+    ]);
+
+    assert!(
+        output.status.success(),
+        "{}",
+        String::from_utf8_lossy(&output.stderr)
+    );
+    let patches_dir = fixture.home().join(".spectral/patches");
+    assert_eq!(
+        String::from_utf8_lossy(&output.stdout).trim(),
+        patches_dir.display().to_string()
+    );
+    assert!(patches_dir.join("series.toml").is_file());
+    assert!(patches_dir.join("0000-cover-letter.patch").is_file());
+}