What causes "the remembered branch changed while preparing to attach" in GitoxideLabs/gitoxide?

Retry the attach after the branch stops changing.

the remembered branch changed while preparing to attach

Error message

the remembered branch changed while preparing to attach

What it means

The remembered branch reference itself changed: its commit id no longer equals `remembered.branch_tip` at validation time. The library refuses to attach because attaching would restore a branch state that no longer matches what was captured. This is the final staleness check in `validate_attach`.

Solutions

Retry the attach after the branch stops changing.
Stop concurrent processes (pull/rebase/CI) touching this branch, then re-run.
Restart the flow to re-remember the branch tip if the new tip is acceptable.

Defensive patterns

Strategy: retry

Try / catch

match attach_reporting(...) {
    Err(e) if e.to_string().contains("remembered branch changed while preparing") => {
        // stop concurrent writers, then re-run the flow
        restart_attach_flow()?;
    }
    other => other?,
}

Prevention

Stop pulls/rebases/CI jobs touching the branch before attaching.
Keep the remember-to-attach window as short as possible.
Verify `git rev-parse refs/heads/<branch>` is stable across the flow.

When it happens

Trigger: Between remembering and validating, someone updated `refs/heads/<branch>` (commit, reset, pull) so `branch_id != remembered.branch_tip`.

Common situations: Another checkout doing a pull/rebase concurrently; a scheduled job pushing to the same local branch; the user manually resetting the branch between operations.

Understand the failure class

Background: "Invalid state transition" errors: "status must be X, actually Y", "already rejected/charging/uninstalled", "cannot ... while running" — what they mean when a library rejects your call — this error's family across 31 libraries.

Related errors

AI-assisted analysis of GitoxideLabs/gitoxide@e73179060b (2026-09-08). Data as JSON: /api/errors/b8afab6996c097c7. Report an issue: GitHub.

Appendix: source

Thrown at gix-tix/src/edit/time_travel.rs:526

    if !head.is_detached() || head.id().map(gix::Id::detach) != Some(head_id) {
        anyhow::bail!("HEAD changed while preparing to attach");
    }
    drop(head);
    let pin = history::all_pins(repository)?
        .into_iter()
        .find(history::Pin::is_head)
        .context("the HEAD pin disappeared while preparing to attach")?;
    if pin.target.try_name() != Some(remembered.branch.as_ref()) || pin.id != remembered.branch_tip {
        anyhow::bail!("the HEAD pin changed while preparing to attach");
    }
    let branch_id = repository
        .find_reference(remembered.branch.as_ref())
        .context("the remembered branch disappeared while preparing to attach")?
        .try_id()
        .context("the remembered branch must be a direct reference")?
        .detach();
    if branch_id != remembered.branch_tip {
        anyhow::bail!("the remembered branch changed while preparing to attach");
    }
    ensure_branch_is_available(repository, remembered.branch.as_ref())
}

#[cfg(test)]
pub(crate) fn attach(
    repository_path: &Path,
    bare: bool,
    revisions: &[OsString],
    include_worktrees: bool,
) -> Result<String> {
    Ok(attach_reporting(repository_path, bare, revisions, include_worktrees)?.0)
}

pub(crate) fn attach_reporting(
    repository_path: &Path,
    bare: bool,
    revisions: &[OsString],

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