actions/checkout@v4 does not fail despite Git reference collision error

[anas-baadshah]

What Happened

In our GitHub Actions workflow, we have a naming collision in remote references (release/12.51.0 vs. release/12.51.0/with-simple-card-changes), which typically causes Git to throw an error:

error: cannot lock ref 'refs/remotes/origin/release/12.51.0/with-simple-card-changes':
'refs/remotes/origin/release/12.51.0' exists; cannot create
'refs/remotes/origin/release/12.51.0/with-simple-card-changes'

Despite this Git error, the actions/checkout@v4 step did not fail. The workflow continued as if the checkout had succeeded, but subsequent steps encountered failures or inconsistent refs.

Expected Behavior

If a Git fetch or checkout operation runs into a reference lock error (or any non-zero exit from Git), we expect the checkout step to fail immediately (return a non-zero exit code). That way, the pipeline knows the repository was not correctly checked out.

Actual Behavior

The checkout step logged an error but did not fail. It exited with a success status, leading to a misleading workflow state.

Environment

Using actions/checkout@v4 in GitHub Actions:

- uses: actions/checkout@v4
  with:
    fetch-depth: 0
    token: ${{ secrets.FULL_ACCESS_TOKEN }}

The repository has (or had) conflicting branch references:
refs/remotes/origin/release/12.51.0 (a file)
refs/remotes/origin/release/12.51.0/with-simple-card-changes (would-be subfolder)

Note: we are not using continue-on-error on checkout step