feat(arch/binary): .PKGINFO parser

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <[email protected]>

internal/arch/binary/pkginfo_test.go

@@ -0,0 +1,135 @@
+package binary
+
+import (
+	"os"
+	"reflect"
+	"strings"
+	"testing"
+)
+
+// readFixture loads a committed .PKGINFO fixture relative to the repo root.
+func readFixture(t *testing.T, path string) string {
+	t.Helper()
+	b, err := os.ReadFile(path)
+	if err != nil {
+		t.Fatalf("read fixture %s: %v", path, err)
+	}
+	return string(b)
+}
+
+func TestPKGInfo(t *testing.T) {
+	tests := []struct {
+		name string
+		src  string
+		want *PKGInfo
+	}{
+		{
+			name: "hello fixture",
+			src:  readFixture(t, "../../../testdata/pkginfo/hello.PKGINFO"),
+			want: &PKGInfo{
+				Name:    "hello",
+				Version: "1.0-1",
+				Desc:    "A tiny demonstration program",
+				URL:     "https://example.org",
+				Arch:    "x86_64",
+				Depends: []string{"glibc", "zlib"},
+			},
+		},
+		{
+			name: "multi fixture",
+			src:  readFixture(t, "../../../testdata/pkginfo/multi.PKGINFO"),
+			want: &PKGInfo{
+				Name:       "multiload",
+				Version:    "2.3-1",
+				Desc:       "Multi dep test",
+				URL:        "https://example.org",
+				Arch:       "x86_64",
+				Depends:    []string{"glibc", "pcre2>=10.42"},
+				OptDepends: []string{"python: for scripting"},
+				Provides:   []string{"multiload"},
+			},
+		},
+		{
+			name: "epoch fixture keeps colon",
+			src:  readFixture(t, "../../../testdata/pkginfo/epoch.PKGINFO"),
+			want: &PKGInfo{
+				Name:    "epochtool",
+				Version: "1:1.0.0-1",
+				Desc:    "Epoch test",
+				URL:     "https://example.org",
+				Arch:    "x86_64",
+				Depends: []string{"glibc"},
+			},
+		},
+		{
+			name: "comments blank lines unknown keys and whitespace",
+			src: strings.Join([]string{
+				"# full-line comment",
+				"",
+				"  pkgname =  spaced  ",
+				"pkgver = 9.9-9",
+				"pkgbase = ignored-base",
+				"license = GPL2",
+				"license = MIT",
+				"builddate = 1724000000",
+				"unknown = whatever",
+				"conflicts = oldtool",
+				"replaces = replaced",
+			}, "\n") + "\n",
+			want: &PKGInfo{
+				Name:      "spaced",
+				Version:   "9.9-9",
+				Conflicts: []string{"oldtool"},
+				Replaces:  []string{"replaced"},
+			},
+		},
+		{
+			name: "last occurrence wins for single-value keys",
+			src:  "pkgname = first\npkgver = 1.0-1\npkgname = second\npkgver = 2.0-2\n",
+			want: &PKGInfo{
+				Name:    "second",
+				Version: "2.0-2",
+			},
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got, err := Parse(tt.src, func(msg string) {
+				t.Errorf("unexpected warn: %s", msg)
+			})
+			if err != nil {
+				t.Fatalf("Parse() error = %v, want nil", err)
+			}
+			if !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("Parse() = %#v, want %#v", got, tt.want)
+			}
+		})
+	}
+}
+
+func TestPKGInfoMalformedLineWarns(t *testing.T) {
+	src := "pkgname = ok\npkgver = 1.0-1\ngarbage no equals\n"
+	var warns []string
+	info, err := Parse(src, func(msg string) {
+		warns = append(warns, msg)
+	})
+	if err != nil {
+		t.Fatalf("Parse() error = %v, want nil", err)
+	}
+	if len(warns) != 1 {
+		t.Fatalf("warn called %d times, want exactly 1: %v", len(warns), warns)
+	}
+	if !strings.Contains(warns[0], "garbage no equals") {
+		t.Errorf("warn message %q does not mention the malformed line", warns[0])
+	}
+	if info.Name != "ok" || info.Version != "1.0-1" {
+		t.Errorf("Parse() = %#v, want name ok / version 1.0-1 despite malformed line", info)
+	}
+}
+
+func TestPKGInfoMissingName(t *testing.T) {
+	_, err := Parse("pkgver = 1.0-1\n", func(string) {})
+	if err == nil {
+		t.Fatal("Parse() error = nil, want error for missing pkgname")
+	}
+}