if (merge_heads.nr > 1)
die(_("Cannot merge multiple branches into empty head."));
return pull_into_void(*merge_heads.sha1, curr_head);
- } else if (opt_rebase) {
- if (merge_heads.nr > 1)
- die(_("Cannot rebase onto multiple branches."));
+ }
+ if (opt_rebase && merge_heads.nr > 1)
+ die(_("Cannot rebase onto multiple branches."));
+
+ if (opt_rebase) {
+ struct commit_list *list = NULL;
+ struct commit *merge_head, *head;
+
+ head = lookup_commit_reference(orig_head);
+ commit_list_insert(head, &list);
+ merge_head = lookup_commit_reference(merge_heads.sha1[0]);
+ if (is_descendant_of(merge_head, list)) {
+ /* we can fast-forward this without invoking rebase */
+ opt_ff = "--ff-only";
+ return run_merge();
+ }
return run_rebase(curr_head, *merge_heads.sha1, rebase_fork_point);
- } else
+ } else {
return run_merge();
+ }
}