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--reroll-count, deleting the superseded revision only once the new one is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.

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}");
+}