refs/files: support symbolic and root refs in initial transaction

The "files" backend has implemented special logic when committing
the first transactions in an otherwise empty ref store: instead of
writing all refs as separate loose files, it instead knows to write them
all into a "packed-refs" file directly. This is significantly more
efficient than having to write each of the refs as separate "loose" ref.

The only user of this optimization is git-clone(1), which only uses this
mechanism to write regular refs. Consequently, the implementation does
not know how to handle both symbolic and root refs. While fine in the
context of git-clone(1), this keeps us from using the mechanism in more
cases.

Adapt the logic to also support symbolic and root refs by using a second
transaction that we use for all of the refs that need to be written as
loose refs.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/refs/files-backend.c b/refs/files-backend.c
index 3ed18475a72aa4798d15b2912c37b4caabd47aac..116d4259697b20583cb2db34ed47025e8781cd42 100644 (file)
--- a/refs/files-backend.c
+++ b/refs/files-backend.c
@@ -2995,6 +2995,7 @@ static int files_transaction_finish_initial(struct files_ref_store *refs,
        int ret = 0;
        struct string_list affected_refnames = STRING_LIST_INIT_NODUP;
        struct ref_transaction *packed_transaction = NULL;
+       struct ref_transaction *loose_transaction = NULL;
 
        assert(err);
 
@@ -3040,6 +3041,7 @@ static int files_transaction_finish_initial(struct files_ref_store *refs,
                if ((update->flags & REF_HAVE_OLD) &&
                    !is_null_oid(&update->old_oid))
                        BUG("initial ref transaction with old_sha1 set");
+
                if (refs_verify_refname_available(&refs->base, update->refname,
                                                  &affected_refnames, NULL,
                                                  err)) {
@@ -3048,26 +3050,48 @@ static int files_transaction_finish_initial(struct files_ref_store *refs,
                }
 
                /*
-                * Add a reference creation for this reference to the
-                * packed-refs transaction:
+                * packed-refs don't support symbolic refs and root refs, so we
+                * have to queue these references via the loose transaction.
                 */
-               ref_transaction_add_update(packed_transaction, update->refname,
-                                          update->flags & ~REF_HAVE_OLD,
-                                          &update->new_oid, &update->old_oid,
-                                          NULL, NULL, NULL);
+               if (update->new_target || is_root_ref(update->refname)) {
+                       if (!loose_transaction) {
+                               loose_transaction = ref_store_transaction_begin(&refs->base, 0, err);
+                               if (!loose_transaction) {
+                                       ret = TRANSACTION_GENERIC_ERROR;
+                                       goto cleanup;
+                               }
+                       }
+
+                       ref_transaction_add_update(loose_transaction, update->refname,
+                                                  update->flags & ~REF_HAVE_OLD,
+                                                  update->new_target ? NULL : &update->new_oid, NULL,
+                                                  update->new_target, NULL, NULL);
+               } else {
+                       ref_transaction_add_update(packed_transaction, update->refname,
+                                                  update->flags & ~REF_HAVE_OLD,
+                                                  &update->new_oid, &update->old_oid,
+                                                  NULL, NULL, NULL);
+               }
        }
 
-       if (packed_refs_lock(refs->packed_ref_store, 0, err)) {
+       if (packed_refs_lock(refs->packed_ref_store, 0, err) ||
+           ref_transaction_commit(packed_transaction, err)) {
                ret = TRANSACTION_GENERIC_ERROR;
                goto cleanup;
        }
+       packed_refs_unlock(refs->packed_ref_store);
 
-       if (ref_transaction_commit(packed_transaction, err)) {
-               ret = TRANSACTION_GENERIC_ERROR;
+       if (loose_transaction) {
+               if (ref_transaction_prepare(loose_transaction, err) ||
+                   ref_transaction_commit(loose_transaction, err)) {
+                       ret = TRANSACTION_GENERIC_ERROR;
+                       goto cleanup;
+               }
        }
 
-       packed_refs_unlock(refs->packed_ref_store);
 cleanup:
+       if (loose_transaction)
+               ref_transaction_free(loose_transaction);
        if (packed_transaction)
                ref_transaction_free(packed_transaction);
        transaction->state = REF_TRANSACTION_CLOSED;