Function isFastForward

remote.go:1123–1154

(s storer.EncodedObjectStorer, old, new plumbing.Hash, earliestShallow *plumbing.Hash)

}

func isFastForward(s storer.EncodedObjectStorer, old, new plumbing.Hash, earliestShallow *plumbing.Hash) (bool, error) {
	c, err := object.GetCommit(s, new)
	if err != nil {
		return false, err
	}

	parentsToIgnore := []plumbing.Hash{}
	if earliestShallow != nil {
		earliestCommit, err := object.GetCommit(s, *earliestShallow)
		if err != nil {
			return false, err
		}

		parentsToIgnore = earliestCommit.ParentHashes
	}

	found := false
	// stop iterating at the earliest shallow commit, ignoring its parents
	// note: when pull depth is smaller than the number of new changes on the remote, this fails due to missing parents.
	//       as far as i can tell, without the commits in-between the shallow pull and the earliest shallow, there's no
	//       real way of telling whether it will be a fast-forward merge.
	iter := object.NewCommitPreorderIter(c, nil, parentsToIgnore)
	err = iter.ForEach(func(c *object.Commit) error {
		if c.Hash != old {
			return nil
		}

		found = true
		return storer.ErrStop
	})
	return found, err
}

func (r *Remote) newUploadPackRequest(o *FetchOptions,
	ar *packp.AdvRefs) (*packp.UploadPackRequest, error) {