[PORT] Fix git error handling (gitea#32401)

---
Conflict resolution: Trivial, for `repo_attributes.go` move where the
`IsErrCanceledOrKilled` needs to happen because of other changes that
happened in this file.

To add some words to this change: It seems to be mostly simplifying the
error handling of git operations.

(cherry picked from commit e524f63d58900557d7d57fc3bcd19d9facc8b8ee)

services/gitdiff/gitdiff.go

@@ -1159,7 +1159,7 @@ func GetDiff(ctx context.Context, gitRepo *git.Repository, opts *DiffOptions, fi
 			Dir:     repoPath,
 			Stdout:  writer,
 			Stderr:  stderr,
-		}); err != nil {
+		}); err != nil && !git.IsErrCanceledOrKilled(err) {
 			log.Error("error during GetDiff(git diff dir: %s): %v, stderr: %s", repoPath, err, stderr.String())
 		}