git "remote error: upload-pack: not our ref" in CI

A shallow fetch requested one exact commit, but by the time the request reached the server that SHA was no longer an advertised ref, so upload-pack refuses it as "not our ref". This is typically a force-push happening between event and fetch, and a retry usually resolves it.

What this error means

A fetch of a pinned SHA fails with "fatal: remote error: upload-pack: not our ref <sha>". It appears intermittently, often only when the branch was force-pushed near the run.

git

fatal: remote error: upload-pack: not our ref 4b825dc642cb6eb9a060e54bf8d69288fbee4904

Common causes

A force-push removed the commit mid-run

The queued run pinned a SHA; a force-push then rewrote the branch so the server no longer advertises that exact commit, and upload-pack rejects the request.

Fetching an unadvertised object by SHA

The remote only serves reachable, advertised commits by default; a SHA that is not the tip of any ref may be refused.

How to fix it

Retry the fetch

Because the cause is a timing race, retrying (or re-running) after the branch settles usually succeeds.

Terminal

for i in 1 2 3; do git fetch --depth 1 origin "$SHA" && break || sleep 5; done

Fetch the branch tip instead of a stale SHA

Check out the current branch head rather than a pinned SHA that may have been rewritten.

.github/workflows/ci.yml

- uses: actions/checkout@v4
  with:
    ref: ${{ github.ref }}
    fetch-depth: 0

How to prevent it

Avoid force-pushing branches with runs in flight.
Retry a "not our ref" fetch; it is usually transient.
Prefer the branch tip over a possibly rewritten SHA.