As a follow-up to the parent of this commit, it was found that not
checking for the existence of blobs linked from trees sped up the fetch
from 24m47.815s to 2m2.127s. Teach Git to do that.
The tradeoff of not checking blobs is documented in a code comment.
(Blobs may also be linked from tag objects, but it is impossible to know
the type of an object linked from a tag object without looking it up in
the object database, so the code for that is untouched.)
Signed-off-by: Jonathan Tan <jonathantanmy@xxxxxxxxxx>
---
builtin/index-pack.c | 29 ++++++++++++++++++++++++++++-
1 file changed, 28 insertions(+), 1 deletion(-)
diff --git a/builtin/index-pack.c b/builtin/index-pack.c
index d1c777a6af..57b7888c42 100644
--- a/builtin/index-pack.c
+++ b/builtin/index-pack.c
@@ -817,6 +817,33 @@ static void record_outgoing_link(const struct object_id *oid)
oidset_insert(&outgoing_links, oid);
}
+static void maybe_record_name_entry(const struct name_entry *entry)
+{
+ /*
+ * The benefit of doing this is as above (fetch speedup), but the drawback
+is that if the packfile to be indexed references a local blob directly
+(that is, not through a local tree), that local blob is in danger of
+being garbage collected. Such a situation may arise if we push local
+commits, including one with a change to a blob in the root tree,
+and then the server incorporates them into its main branch through a
+"rebase" or "squash" merge strategy, and then we fetch the new main
+branch from the server.
+
+This situation has not been observed yet - we have only noticed missing
+commits, not missing trees or blobs. (In fact, if it were believed that
+only missing commits are problematic, one could argue that we should
+also exclude trees during the outgoing link check; but it is safer to
+include them.)
+
+Due to the rarity of the situation (it has not been observed to happen
+in real life), and because the "penalty" in such a situation is merely
+to refetch the missing blob when it's needed, the tradeoff seems
+worth it.
+ */
+ if (S_ISDIR(entry->mode))
+ record_outgoing_link(&entry->oid);
+}
+
static void do_record_outgoing_links(struct object *obj)
{
if (obj->type == OBJ_TREE) {
@@ -831,7 +858,7 @@ static void do_record_outgoing_links(struct object *obj)
*/
return;
while (tree_entry_gently(&desc, &entry))
- record_outgoing_link(&entry.oid);
+ maybe_record_name_entry(&entry);
} else if (obj->type == OBJ_COMMIT) {
struct commit *commit = (struct commit *) obj;
struct commit_list *parents = commit->parents;
--
2.47.0.338.g60cca15819-goog
