[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)

routers/web/repo/githttp.go

@@ -467,7 +467,7 @@ func serviceRPC(ctx *context.Context, h *serviceHandler, service string) {
 		Stderr:            &stderr,
 		UseContextTimeout: true,
 	}); err != nil {
-		if err.Error() != "signal: killed" {
+		if !git.IsErrCanceledOrKilled(err) {
 			log.Error("Fail to serve RPC(%s) in %s: %v - %s", service, h.getRepoDir(), err, stderr.String())
 		}
 		return