pull: refactor fast-forward check

We would like to be able to make this check before the decision to
rebase is made in a future step.  Besides, using a separate helper
makes the code easier to follow.

Signed-off-by: Felipe Contreras <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: felipec

builtin/pull.c

@@ -924,6 +924,20 @@ static int run_rebase(const struct object_id *newbase,
 	return ret;
 }
 
+static int get_can_ff(struct object_id *orig_head, struct object_id *orig_merge_head)
+{
+	int ret;
+	struct commit_list *list = NULL;
+	struct commit *merge_head, *head;
+
+	head = lookup_commit_reference(the_repository, orig_head);
+	commit_list_insert(head, &list);
+	merge_head = lookup_commit_reference(the_repository, orig_merge_head);
+	ret = repo_is_descendant_of(the_repository, merge_head, list);
+	free_commit_list(list);
+	return ret;
+}
+
 int cmd_pull(int argc, const char **argv, const char *prefix)
 {
 	const char *repo, **refspecs;
@@ -1040,22 +1054,12 @@ int cmd_pull(int argc, const char **argv, const char *prefix)
 		    submodule_touches_in_range(the_repository, &upstream, &curr_head))
 			die(_("cannot rebase with locally recorded submodule modifications"));
 		if (!autostash) {
-			struct commit_list *list = NULL;
-			struct commit *merge_head, *head;
-
-			head = lookup_commit_reference(the_repository,
-						       &orig_head);
-			commit_list_insert(head, &list);
-			merge_head = lookup_commit_reference(the_repository,
-							     &merge_heads.oid[0]);
-			if (repo_is_descendant_of(the_repository,
-						  merge_head, list)) {
+			if (get_can_ff(&orig_head, &merge_heads.oid[0])) {
 				/* we can fast-forward this without invoking rebase */
 				opt_ff = "--ff-only";
 				ran_ff = 1;
 				ret = run_merge();
 			}
-			free_commit_list(list);
 		}
 		if (!ran_ff)
 			ret = run_rebase(&newbase, &upstream);