Block git option injection via base ref and handle non-ASCII paths

The caller-supplied base ref of detect_changes/get_affected_flows sat
before "--" with no validation, so values like --output=<path> were
parsed as git diff options. Reject refs starting with '-' and add the
"--" separator to ChangedFiles.

Also run diff with core.quotePath=false: quoted octal output for
non-ASCII paths broke hunk-to-file attribution and file matching.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: tae2089

internal/analysis/changes/git.go

@@ -37,7 +37,10 @@ func NewExecGitClient() *ExecGitClient {
 // @requires repoDir points to a valid git working tree
 // @ensures returned file paths are trimmed and exclude blank lines
 func (g *ExecGitClient) ChangedFiles(ctx context.Context, repoDir, baseRef string) ([]string, error) {
-	out, err := runGitLimited(ctx, repoDir, []string{"diff", "--name-only", baseRef})
+	if err := validateBaseRef(baseRef); err != nil {
+		return nil, err
+	}
+	out, err := runGitLimited(ctx, repoDir, []string{"-c", "core.quotePath=false", "diff", "--name-only", baseRef, "--"})
 	if err != nil {
 		return nil, trace.Wrap(err, "git diff --name-only")
 	}
@@ -66,7 +69,10 @@ func (g *ExecGitClient) ChangedFiles(ctx context.Context, repoDir, baseRef strin
 // @requires repoDir points to a valid git working tree
 // @ensures each returned hunk has a file path and inclusive start/end lines
 func (g *ExecGitClient) DiffHunks(ctx context.Context, repoDir, baseRef string, paths []string) ([]Hunk, error) {
-	args := []string{"diff", "-U0", baseRef, "--"}
+	if err := validateBaseRef(baseRef); err != nil {
+		return nil, err
+	}
+	args := []string{"-c", "core.quotePath=false", "diff", "-U0", baseRef, "--"}
 	args = append(args, paths...)
 	out, err := runGitLimited(ctx, repoDir, args)
 	if err != nil {
@@ -98,6 +104,19 @@ func (g *ExecGitClient) DiffHunks(ctx context.Context, repoDir, baseRef string,
 	return hunks, nil
 }
 
+// validateBaseRef rejects base revisions that git would parse as command options.
+// @intent block git argument injection through the caller-supplied base ref, which sits
+// before the "--" separator and would otherwise be interpreted as a diff flag.
+func validateBaseRef(baseRef string) error {
+	if baseRef == "" {
+		return fmt.Errorf("base ref must not be empty")
+	}
+	if strings.HasPrefix(baseRef, "-") {
+		return fmt.Errorf("invalid base ref %q: must not start with '-'", baseRef)
+	}
+	return nil
+}
+
 // runGitLimited runs a git subcommand with the default output size cap.
 // @intent share a single bounded git invocation helper across diff operations
 func runGitLimited(ctx context.Context, repoDir string, args []string) ([]byte, error) {

internal/analysis/changes/git_test.go

@@ -29,6 +29,46 @@ func TestGitClient_ChangedFiles(t *testing.T) {
 	}
 }
 
+func TestGitClient_RejectsOptionLikeBaseRef(t *testing.T) {
+	dir := initTestRepo(t)
+	writeFile(t, dir, "hello.go", "package main\n")
+	gitCommit(t, dir, "initial")
+
+	git := NewExecGitClient()
+	for _, base := range []string{"--output=/tmp/pwned", "-U9999", "--no-index"} {
+		if _, err := git.ChangedFiles(context.Background(), dir, base); err == nil {
+			t.Errorf("ChangedFiles accepted option-like base %q", base)
+		}
+		if _, err := git.DiffHunks(context.Background(), dir, base, []string{"hello.go"}); err == nil {
+			t.Errorf("DiffHunks accepted option-like base %q", base)
+		}
+	}
+}
+
+func TestGitClient_ChangedFiles_NonASCIIPath(t *testing.T) {
+	dir := initTestRepo(t)
+	writeFile(t, dir, "한글.go", "package main\n")
+	gitCommit(t, dir, "initial")
+	writeFile(t, dir, "한글.go", "package main\n\nfunc Hello() {}\n")
+
+	git := NewExecGitClient()
+	files, err := git.ChangedFiles(context.Background(), dir, "HEAD")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(files) != 1 || files[0] != "한글.go" {
+		t.Fatalf("expected unquoted 한글.go, got %v", files)
+	}
+
+	hunks, err := git.DiffHunks(context.Background(), dir, "HEAD", []string{"한글.go"})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(hunks) == 0 || hunks[0].FilePath != "한글.go" {
+		t.Fatalf("expected hunk for unquoted 한글.go, got %+v", hunks)
+	}
+}
+
 func TestGitClient_DiffHunks(t *testing.T) {
 	dir := initTestRepo(t)
 	writeFile(t, dir, "hello.go", "package main\n\nfunc Old() {}\n")