pub async fn advance_local_branch(repo_dir: &Path, branch: &str) -> Result<()>Expand description
Advance the local branch ref to match origin/<branch> after a fetch.
If the branch is currently checked out, uses merge --ff-only so the
working tree stays in sync. Otherwise updates the ref directly after
verifying the move is a fast-forward. Errors are non-fatal for the
pipeline (which only needs origin/<branch>), but keeping the local
branch current avoids surprise “behind by N commits” messages.