fix: fetch revision only then fallback to default refspec (#5605)

* fix: fallback to fetch default only on error

Ignoring commit SHA breaks gerrit when the commit is not merged

Signed-off-by: Yujun Zhang <yujunz@nvidia.com>

* revert util/git/client.go changes

Signed-off-by: Alexander Matyushentsev <AMatyushentsev@gmail.com>

Co-authored-by: Alexander Matyushentsev <AMatyushentsev@gmail.com>

reposerver/repository/repository.go

@@ -1583,25 +1583,25 @@ func checkoutRevision(gitClient git.Client, revision string) error {
 		return status.Errorf(codes.Internal, "Failed to initialize git repo: %v", err)
 	}
 
-	// Some git providers don't support fetching commit sha
-	if revision != "" && !git.IsCommitSHA(revision) && !git.IsTruncatedCommitSHA(revision) {
-		err = gitClient.Fetch(revision)
-		if err != nil {
-			return status.Errorf(codes.Internal, "Failed to fetch %s: %v", revision, err)
-		}
-		err = gitClient.Checkout("FETCH_HEAD")
-		if err != nil {
-			return status.Errorf(codes.Internal, "Failed to checkout FETCH_HEAD: %v", err)
-		}
-	} else {
+	err = gitClient.Fetch(revision)
+
+	if err != nil {
+		log.Infof("Failed to fetch revision %s: %v", revision, err)
+		log.Infof("Fallback to fetch default")
 		err = gitClient.Fetch("")
 		if err != nil {
-			return status.Errorf(codes.Internal, "Failed to fetch %s: %v", revision, err)
+			return status.Errorf(codes.Internal, "Failed to fetch default: %v", err)
 		}
 		err = gitClient.Checkout(revision)
 		if err != nil {
-			return status.Errorf(codes.Internal, "Failed to checkout %s: %v", revision, err)
+			return status.Errorf(codes.Internal, "Failed to checkout revision %s: %v", revision, err)
 		}
+		return err
+	}
+
+	err = gitClient.Checkout("FETCH_HEAD")
+	if err != nil {
+		return status.Errorf(codes.Internal, "Failed to checkout FETCH_HEAD: %v", err)
 	}
 
 	return err