fix(diff): propagate untracked file listing errors (#1140)

* fix(diff): propagate untracked file listing errors

* test: Apply suggestion from @lizhengfeng101

---------

Co-authored-by: Kite <254839944+lizhengfeng101@users.noreply.github.com>

internal/diff/git.go

@@ -620,8 +620,11 @@ func (p *Provider) untrackedFileDiffs(ctx context.Context) ([]string, error) {
 }
 
 func (p *Provider) untrackedFilesList(ctx context.Context) ([]string, error) {
-	out, err := p.runGit(ctx, "-c", "core.quotepath=false", "ls-files", "--others", "--exclude-standard")
-	if err != nil || out == "" {
+	out, stderr, err := p.runGitSplit(ctx, "-c", "core.quotepath=false", "ls-files", "--others", "--exclude-standard")
+	if err != nil {
+		return nil, gitFailure("git ls-files", stderr, err)
+	}
+	if out == "" {
 		return nil, nil
 	}
 	patterns := p.loadGitignorePatterns()

internal/diff/git_error_test.go

@@ -134,6 +134,27 @@ func TestGetDiff_WorkspaceFailureSurfacesFallbackMessage(t *testing.T) {
 	}
 }
 
+// TestUntrackedFilesListPropagatesGitFailure separates the two cases the old
+// `if err != nil || out == ""` folded together: a repository with no untracked
+// files, and git failing to enumerate them at all. The second one used to
+// return an empty list, so a workspace review carried on with the untracked
+// half of its input missing and no way for the caller to notice.
+func TestUntrackedFilesListPropagatesGitFailure(t *testing.T) {
+	repo := filepath.Join(t.TempDir(), "missing-repo")
+
+	provider := NewWorkspaceProvider(repo, nil)
+
+	_, err := provider.untrackedFilesList(context.Background())
+	if err == nil {
+		t.Fatal("expected untrackedFilesList to return git error")
+	}
+	// Pins gitFailure rather than any error: a bare fmt.Errorf would satisfy the
+	// check above while dropping git's own diagnosis, which is the #972 regression.
+	if got := err.Error(); !strings.Contains(got, "git ls-files failed") {
+		t.Errorf("error %q lost the operation name", got)
+	}
+}
+
 // shimGit puts a fake `git` at the front of PATH for the duration of the test.
 func shimGit(t *testing.T, body string) {
 	t.Helper()