handle lock file deletion before checkoputRevision

Signed-off-by: reggie-k <regina.voloshin@codefresh.io>

Author: reggie-k

reposerver/repository/repository.go

@@ -2533,7 +2533,25 @@ func fetch(gitClient git.Client, targetRevisions []string) error {
 	return nil
 }
 
+// removeStaleGitLocks best-effort removes common stale git lock files in the repository.
+// It is safe to call while holding the per-repo lock and before running any git commands.
+
+func removeStaleGitLocks(repoRoot string) {
+	path := filepath.Join(repoRoot, ".git", "HEAD.lock")
+	log.Infof("Checking whether HEAD.lock exists %s", path)
+	if _, err := os.Stat(path); err == nil {
+		log.Warnf("HEAD.lock present in git repository %s, removing it", repoRoot)
+		if rmErr := os.Remove(path); rmErr == nil {
+			log.Infof("Removed stale git lock %s", path)
+		} else if !os.IsNotExist(rmErr) {
+			log.Warnf("Failed to remove git lock %s: %v", path, rmErr)
+		}
+	}
+}
+
 func checkoutRevision(gitClient git.Client, revision string, submoduleEnabled bool) error {
+	removeStaleGitLocks(gitClient.Root())
+
 	err := gitClient.Init()
 	if err != nil {
 		return status.Errorf(codes.Internal, "Failed to initialize git repo: %v", err)

reposerver/repository/repository_test.go

@@ -3016,6 +3016,29 @@ func TestInit(t *testing.T) {
 	initGitRepo(t, newGitRepoOptions{path: path.Join(dir, "repo2"), remote: "https://github.com/argo-cd/test-repo2", createPath: true, addEmptyCommit: false})
 }
 
+func TestRemoveStaleGitHeadLock(t *testing.T) {
+	dir := t.TempDir()
+	// create a fake repo structure with .git/HEAD.lock
+	gitDir := path.Join(dir, ".git")
+	require.NoError(t, os.MkdirAll(gitDir, 0o755))
+	headLock := path.Join(gitDir, "HEAD.lock")
+	require.NoError(t, os.WriteFile(headLock, []byte("test"), 0o644))
+
+	// sanity: lock exists before
+	_, err := os.Stat(headLock)
+	require.NoError(t, err)
+
+	removeStaleGitLocks(dir)
+
+	// lock should be gone after cleanup
+	_, err = os.Stat(headLock)
+	require.Error(t, err)
+	require.True(t, os.IsNotExist(err))
+
+	// calling again should be a no-op (no error)
+	removeStaleGitLocks(dir)
+}
+
 // TestCheckoutRevisionCanGetNonstandardRefs shows that we can fetch a revision that points to a non-standard ref. In
 // other words, we haven't regressed and caused this issue again: https://github.com/argoproj/argo-cd/issues/4935
 func TestCheckoutRevisionCanGetNonstandardRefs(t *testing.T) {
@@ -3057,6 +3080,7 @@ func TestCheckoutRevisionPresentSkipFetch(t *testing.T) {
 
 	gitClient := &gitmocks.Client{}
 	gitClient.On("Init").Return(nil)
+	gitClient.On("Root").Return("<repo-root>")
 	gitClient.On("IsRevisionPresent", revision).Return(true)
 	gitClient.On("Checkout", revision, mock.Anything).Return("", nil)
 
@@ -3069,6 +3093,7 @@ func TestCheckoutRevisionNotPresentCallFetch(t *testing.T) {
 
 	gitClient := &gitmocks.Client{}
 	gitClient.On("Init").Return(nil)
+	gitClient.On("Root").Return("<repo-root>")
 	gitClient.On("IsRevisionPresent", revision).Return(false)
 	gitClient.On("Fetch", "").Return(nil)
 	gitClient.On("Checkout", revision, mock.Anything).Return("", nil)
@@ -3083,6 +3108,7 @@ func TestFetch(t *testing.T) {
 
 	gitClient := &gitmocks.Client{}
 	gitClient.On("Init").Return(nil)
+	gitClient.On("Root").Return("<repo-root>")
 	gitClient.On("IsRevisionPresent", revision1).Once().Return(true)
 	gitClient.On("IsRevisionPresent", revision2).Once().Return(false)
 	gitClient.On("Fetch", "").Return(nil)