nonfastforward

Nonfastforward, often written as non-fast-forward, is a term used in Git and other distributed version control systems to describe a branch update that cannot be performed by a simple forward move of the branch pointer. In Git this occurs when the history of the remote branch has diverged from the local history, so there is no fast-forward path from the remote tip to the new commit.

In practical terms, a non-fast-forward situation arises most commonly during pushes. If the remote repository contains commits that you do not have locally, pushing your commits would require rewriting the remote history. Because this could discard others’ work, Git rejects the update and reports a non-fast-forward error. The same concept applies during pulls or fetches when the local branch would need a merge or a rebase to incorporate remote changes.

Common causes include collaborative workflows where multiple people push to the same branch, rebasing local commits, or history rewrites on the remote (for example after a rebase). The usual responses are to integrate remote changes into the local branch, rather than overwriting them, or to carefully force an update only with proper safeguards.

Ways to resolve a nonfastforward situation:

- Fetch the latest remote changes and merge: git fetch origin; git merge origin/branch, or git pull.

- Rebase your local commits on top of the updated remote: git fetch origin; git rebase origin/branch, then push.

- If you intentionally want to overwrite the remote (use with caution): git push --force-with-lease to prevent overwriting others’ work.

Nonfastforward is a normal condition in collaborative workflows and is not a bug; it signals that history has diverged and requires explicit action to reconcile.