The can_fast_forward() function is potentially much more expensive
than is_interactive() since it e.g. might need to call
is_linear_history().
So reversing the two looks like an obvious improvement, but doing so
reveals a previously hidden caveat: We need the can_fast_forward()
function to populate data used later, namely the "merge_bases"
variable. This has been the case since it was added in
9a48a615b4 ("builtin rebase: try to fast forward when possible",
2018-09-04).
So let's refactor it into two functions. Now we'll always call
populate_merge_bases(), and then only call can_fast_forward() if
is_interactive() is false, making this both faster in pathological
cases, and more importantly easier to follow.
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@xxxxxxxxx>
---
builtin/rebase.c | 41 +++++++++++++++++++++++++++--------------
1 file changed, 27 insertions(+), 14 deletions(-)
diff --git a/builtin/rebase.c b/builtin/rebase.c
index ae6b9b42b8..cb5d7fcb53 100644
--- a/builtin/rebase.c
+++ b/builtin/rebase.c
@@ -878,24 +878,30 @@ static int is_linear_history(struct commit *from, struct commit *to)
return 1;
}
-static int can_fast_forward(struct commit *onto, struct commit *upstream,
+static void populate_merge_bases(struct commit *head, struct commit *onto,
+ struct commit_list *merge_bases,
+ struct object_id *merge_base)
+{
+ merge_bases = get_merge_bases(onto, head);
+ if (!merge_bases || merge_bases->next) {
+ oidcpy(merge_base, &null_oid);
+ return;
+ }
+ oidcpy(merge_base, &merge_bases->item->object.oid);
+}
+
+static int can_fast_forward(struct commit *head,
+ struct commit *onto, struct commit *upstream,
struct commit *restrict_revision,
- struct object_id *head_oid, struct object_id *merge_base)
+ struct object_id *head_oid,
+ struct commit_list *merge_bases,
+ struct object_id *merge_base)
{
- struct commit *head = lookup_commit(the_repository, head_oid);
- struct commit_list *merge_bases = NULL;
int res = 0;
if (!head)
goto done;
- merge_bases = get_merge_bases(onto, head);
- if (!merge_bases || merge_bases->next) {
- oidcpy(merge_base, &null_oid);
- goto done;
- }
-
- oidcpy(merge_base, &merge_bases->item->object.oid);
if (!oideq(merge_base, &onto->object.oid))
goto done;
@@ -1154,6 +1160,8 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
OPT_END(),
};
int i;
+ struct commit *head_commit;
+ struct commit_list *merge_bases = NULL;
if (argc == 2 && !strcmp(argv[1], "-h"))
usage_with_options(builtin_rebase_usage,
@@ -1703,9 +1711,14 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
* with new commits recreated by replaying their changes. This
* optimization must not be done if this is an interactive rebase.
*/
- if (can_fast_forward(options.onto, options.upstream, options.restrict_revision,
- &options.orig_head, &merge_base) &&
- !is_interactive(&options)) {
+ head_commit = lookup_commit(the_repository, &options.orig_head);
+ if (head_commit)
+ populate_merge_bases(head_commit, options.onto, merge_bases,
+ &merge_base);
+ if (!is_interactive(&options) &&
+ can_fast_forward(head_commit, options.onto, options.upstream,
+ options.restrict_revision, &options.orig_head,
+ merge_bases, &merge_base)) {
int flag;
if (!(options.flags & REBASE_FORCE)) {
--
2.21.0.1020.gf2820cf01a
