dagger/dagger · error

error getting reference %q: %w

Error message

error getting reference %q: %w

What it means

After a successful `git fetch`, fetchRef looks up the fetched reference with go-git's repo.Reference(plumbing.ReferenceName(dest), true). If the ref cannot be resolved, the error is wrapped as "error getting reference %q: %w" with the destination ref name. This means the fetch succeeded but the expected local ref was not created or cannot be resolved.

Source

Thrown at engine/telemetry/labels.go:607

	// breaking subsequent git history operations (merge-base, describe, ...).
	args := []string{"fetch"}
	if isShallowRepo(workdir) {
		args = append(args, "--depth", "1")
	}
	args = append(args, remote, fmt.Sprintf("+%s:%s", src, dest))

	// Fetch from the origin remote
	cmd := exec.Command("git", args...)
	cmd.Dir = workdir
	out, err := cmd.CombinedOutput()
	if err != nil {
		return nil, fmt.Errorf("error fetching branch from origin: %w\n%s", err, string(out))
	}

	// Get the reference of the fetched branch
	ref, err := repo.Reference(plumbing.ReferenceName(dest), true)
	if err != nil {
		return nil, fmt.Errorf("error getting reference %q: %w", dest, err)
	}

	// Get the commit object of the fetched branch
	branchCommit, err := repo.CommitObject(ref.Hash())
	if err != nil {
		return nil, fmt.Errorf("error getting commit %q: %w", ref.Hash(), err)
	}

	// Cleanup the temp ref
	cmd = exec.Command("git", "update-ref", "-d", dest, ref.Hash().String())
	cmd.Dir = workdir
	out, err = cmd.CombinedOutput()
	if err != nil {
		err = fmt.Errorf("error deleting ref %q: %w\n%s", dest, err, out)
		slog.Warn("failed to cleanup temp ref", "err", err)
	}

	return branchCommit, nil

View on GitHub (pinned to 82ba2681db)

Solutions

1. Compare the %q ref name in the error with the actual refs (`git show-ref | grep <name>`) in the workdir.
2. Ensure the git fetch refspec actually writes to the `dest` reference used in the lookup.
3. Run `go-git` storage refresh or re-open the repository after external git commands.
4. Validate the ref name format before calling (e.g. refs/remotes/origin/<branch>).

Example fix

// before
ref, err := repo.Reference(plumbing.ReferenceName(dest), true)
// after (fallback lookup)
ref, err := repo.Reference(plumbing.ReferenceName(dest), true)
if err != nil {
    ref, err = repo.Reference(plumbing.ReferenceName("refs/remotes/origin/"+branch), true)
}

// confirm ref naming before lookup
func validRemoteRef(branch string) bool {
    return strings.HasPrefix(branch, "refs/") || branch != ""
}

ref, err := repo.Reference(plumbing.ReferenceName(dest), true)
if err != nil {
    slog.Warn("ref not found after fetch", "dest", dest)
    return nil, err // or fall back to another ref naming scheme
}

When it happens

Trigger: repo.Reference(dest, true) fails right after fetching — dest ref name doesn't match what the fetch wrote, the fetch refspec mapped elsewhere, or a shallow/partial clone omitted the ref.

Common situations: Mismatch between the fetch destination and the ref name looked up; go-git ref storage out of sync after external git commands mutated .git; empty or invalid ref name derived from the PR head.

Related errors

• invalid git-latest ref %q
• failed to delete tmp ref: %w
• error getting commit %q: %w
• failed to generate patch: %w
• remove temporary octopus merge git repository: %w

AI-assisted analysis of dagger/dagger@82ba2681db (2026-09-05). Data as JSON: /api/errors/c0c681e76f8c97fb. Report an issue: GitHub.