Re: [PATCH 2/2] completion: silence pseudoref existence check

> In 44dbb3bf29 (completion: support pseudoref existence checks for
> reftables, 2023-12-19), we have extended the Bash completion script to
> support future ref backends better by using git-rev-parse(1) to check
> for pseudo-ref existence. This conversion has introduced a bug, because
> even though we pass `--quiet` to git-rev-parse(1) it would still output
> the resolved object ID of the ref in question if it exists.
>
> Fix this by redirecting its stdout to `/dev/null` and add a test that
> catches this behaviour. Note that the test passes even without the fix
> for the "files" backend because we parse pseudo refs via the filesystem
> directly in that case. But the test will fail with the "reftable"
> backend.