fix(knight): strip show-prefix from rename dst side in gitStatusSnapshot (#2755)

internal/knight/project_proposal.go

@@ -134,8 +134,18 @@ func gitStatusSnapshot(dir string) string {
 	var b strings.Builder
 	for _, line := range strings.Split(string(out), "\n") {
 		if len(line) > 3 && strings.HasPrefix(line[3:], prefix) {
+			rest := strings.TrimPrefix(line[3:], prefix)
+			// #2755: a staged rename reads "R old -> new" and BOTH sides are
+			// root-relative. The old whole-line strip left the dst side
+			// prefixed ("R .ggcode/a.md -> mobile/.ggcode/b.md"), so the pure
+			// .ggcode rename exemption (which requires both sides in .ggcode)
+			// failed in monorepo subdirs and fired a false guardrail
+			// violation. Strip the dst side too.
+			if arrow := strings.Index(rest, " -> "); arrow >= 0 {
+				rest = rest[:arrow] + " -> " + strings.TrimPrefix(rest[arrow+4:], prefix)
+			}
 			b.WriteString(line[:3])
-			b.WriteString(line[3+len(prefix):])
+			b.WriteString(rest)
 		} else {
 			b.WriteString(line)
 		}

internal/knight/zz_issue2755_test.go

@@ -0,0 +1,70 @@
+package knight
+
+// Issue #2755 probe: in a monorepo subdirectory (--show-prefix non-empty),
+// gitStatusSnapshot stripped the show-prefix only from the start of the
+// porcelain line - the rename DST side (after " -> ") kept the prefix, so a
+// pure .ggcode rename read as "R  .ggcode/a.md -> mobile/.ggcode/b.md",
+// failed the BOTH-sides inGG() exemption check, and fired a false
+// READ-ONLY GUARDRAIL VIOLATED. Real-git-repo probe: init a repo, commit a
+// file under <sub>/.ggcode/, git mv it from inside <sub>, snapshot.
+
+import (
+	"os"
+	"os/exec"
+	"path/filepath"
+	"strings"
+	"testing"
+)
+
+func TestIssue2755RenameBothSidesStrippedInSubdir(t *testing.T) {
+	if _, err := exec.LookPath("git"); err != nil {
+		t.Skip("git not available")
+	}
+	repo := t.TempDir()
+	run := func(args ...string) {
+		t.Helper()
+		cmd := exec.Command("git", args...)
+		cmd.Dir = repo
+		if out, err := cmd.CombinedOutput(); err != nil {
+			t.Fatalf("git %v: %v\n%s", args, err, out)
+		}
+	}
+	run("init", "-q")
+	run("config", "user.email", "t@t")
+	run("config", "user.name", "t")
+
+	sub := filepath.Join(repo, "mobile", ".ggcode")
+	if err := os.MkdirAll(sub, 0755); err != nil {
+		t.Fatalf("mkdir: %v", err)
+	}
+	old := filepath.Join(sub, "a.md")
+	if err := os.WriteFile(old, []byte("x"), 0644); err != nil {
+		t.Fatalf("write: %v", err)
+	}
+	run("add", "-A")
+	run("commit", "-qm", "init")
+
+	// git mv from inside the subdir stages a rename (R line in porcelain).
+	mv := exec.Command("git", "mv", ".ggcode/a.md", ".ggcode/b.md")
+	mv.Dir = filepath.Join(repo, "mobile")
+	if out, err := mv.CombinedOutput(); err != nil {
+		t.Fatalf("git mv: %v\n%s", err, out)
+	}
+
+	snap := gitStatusSnapshot(filepath.Join(repo, "mobile"))
+	var renameLine string
+	for _, line := range strings.Split(snap, "\n") {
+		if strings.HasPrefix(line, "R") && strings.Contains(line, "->") {
+			renameLine = line
+		}
+	}
+	if renameLine == "" {
+		t.Fatalf("no staged rename line in snapshot:\n%s", snap)
+	}
+	if strings.Contains(renameLine, "mobile/") {
+		t.Fatalf("rename line keeps show-prefix on a side: %q (want both sides dir-relative)", renameLine)
+	}
+	if renameLine != "R  .ggcode/a.md -> .ggcode/b.md" {
+		t.Fatalf("unexpected normalized rename line: %q", renameLine)
+	}
+}