fix regression in support for detached HEAD state

for gh pr status

command/pr.go

@@ -116,7 +116,7 @@ func prStatus(cmd *cobra.Command, args []string) error {
 	repoOverride, _ := cmd.Flags().GetString("repo")
 	currentPRNumber, currentPRHeadRef, err := prSelectorForCurrentBranch(ctx, baseRepo)
 
-	if err != nil && repoOverride == "" && err.Error() != "git: not on any branch" {
+	if err != nil && repoOverride == "" && err != git.ErrNotOnAnyBranch {
 		return fmt.Errorf("could not query for pull request for current branch: %w", err)
 	}
 

context/context.go

@@ -207,7 +207,11 @@ func (c *fsContext) Branch() (string, error) {
 	}
 
 	currentBranch, err := git.CurrentBranch()
-	if err != nil {
+	switch err {
+	case nil:
+	case git.ErrNotOnAnyBranch:
+		return "", err
+	default:
 		return "", fmt.Errorf("could not determine current branch: %w", err)
 	}
 

git/git.go

@@ -13,6 +13,9 @@ import (
 	"github.com/cli/cli/internal/run"
 )
 
+// ErrNotOnAnyBranch indicates that the users is in detached HEAD state
+var ErrNotOnAnyBranch = errors.New("git: not on any branch")
+
 // Ref represents a git commit reference
 type Ref struct {
 	Hash string
@@ -64,7 +67,7 @@ func CurrentBranch() (string, error) {
 	if errors.As(err, &cmdErr) {
 		if cmdErr.Stderr.Len() == 0 {
 			// Detached head
-			return "", errors.New("git: not on any branch")
+			return "", ErrNotOnAnyBranch
 		}
 	}
 

git/git_test.go

@@ -67,9 +67,8 @@ func Test_CurrentBranch_detached_head(t *testing.T) {
 	if err == nil {
 		t.Errorf("expected an error")
 	}
-	expectedError := "git: not on any branch"
+	if err != ErrNotOnAnyBranch {
-	if err.Error() != expectedError {
+		t.Errorf("got unexpected error: %s instead of %s", err, ErrNotOnAnyBranch)
-		t.Errorf("got unexpected error: %s instead of %s", err.Error(), expectedError)
 	}
 	if len(cs.Calls) != 1 {
 		t.Errorf("expected 1 git call, saw %d", len(cs.Calls))