[PATCH v9 5/9] rebase: refactor can_fast_forward into goto tower

[Denton Liu <liu.denton@xxxxxxxxx>]

Before, can_fast_forward was written with an if-else statement. However,
in the future, we may be adding more termination cases which would lead
to deeply nested if statements.

Refactor to use a goto tower so that future cases can be easily
inserted.

Signed-off-by: Denton Liu <liu.denton@xxxxxxxxx>
---
 builtin/rebase.c | 24 +++++++++++++++---------
 1 file changed, 15 insertions(+), 9 deletions(-)

diff --git a/builtin/rebase.c b/builtin/rebase.c
index 670096c065..22c4f1ff93 100644
--- a/builtin/rebase.c
+++ b/builtin/rebase.c
@@ -1264,21 +1264,27 @@ static int can_fast_forward(struct commit *onto, struct object_id *head_oid,
 			    struct object_id *merge_base)
 {
 	struct commit *head = lookup_commit(the_repository, head_oid);
-	struct commit_list *merge_bases;
-	int res;
+	struct commit_list *merge_bases = NULL;
+	int res = 0;
 
 	if (!head)
-		return 0;
+		goto done;
 
 	merge_bases = get_merge_bases(onto, head);
-	if (merge_bases && !merge_bases->next) {
-		oidcpy(merge_base, &merge_bases->item->object.oid);
-		res = oideq(merge_base, &onto->object.oid);
-	} else {
+	if (!merge_bases || merge_bases->next) {
 		oidcpy(merge_base, &null_oid);
-		res = 0;
+		goto done;
 	}
-	free_commit_list(merge_bases);
+
+	oidcpy(merge_base, &merge_bases->item->object.oid);
+	if (!oideq(merge_base, &onto->object.oid))
+		goto done;
+
+	res = 1;
+
+done:
+	if (merge_bases)
+		free_commit_list(merge_bases);
 	return res && is_linear_history(onto, head);
 }
 
-- 
2.23.0.248.g3a9dd8fb08