refs: skip hooks when deleting uncovered packed refs

When deleting refs from the loose-files refs backend, then we need to be
careful to also delete the same ref from the packed refs backend, if it
exists. If we don't, then deleting the loose ref would "uncover" the
packed ref. We thus always have to queue up deletions of refs for both
the loose and the packed refs backend. This is done in two separate
transactions, where the end result is that the reference-transaction
hook is executed twice for the deleted refs.

This behaviour is quite misleading: it's exposing implementation details
of how the files backend works to the user, in contrast to the logical
updates that we'd really want to expose via the hook. Worse yet, whether
the hook gets executed once or twice depends on how well-packed the
repository is: if the ref only exists as a loose ref, then we execute it
once, otherwise if it is also packed then we execute it twice.

Fix this behaviour and don't execute the reference-transaction hook at
all when refs in the packed-refs backend if it's driven by the files
backend. This works as expected even in case the refs to be deleted only
exist in the packed-refs backend because the loose-backend always queues
refs in its own transaction even if they don't exist such that they can
be locked for concurrent creation. And it also does the right thing in
case neither of the backends has the ref because that would cause the
transaction to fail completely.

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 565929210abedb5cf2f39e8616af8b4fd780c087..844918cbd86026d33cafdbefc1d34688df295261 100644 (file)
--- a/refs/files-backend.c
+++ b/refs/files-backend.c
@@ -1261,7 +1261,8 @@ static int files_delete_refs(struct ref_store *ref_store, const char *msg,
        if (packed_refs_lock(refs->packed_ref_store, 0, &err))
                goto error;
 
-       transaction = ref_store_transaction_begin(refs->packed_ref_store, 0, &err);
+       transaction = ref_store_transaction_begin(refs->packed_ref_store,
+                                                 REF_TRANSACTION_SKIP_HOOK, &err);
        if (!transaction)
                goto error;
 
@@ -2776,7 +2777,8 @@ static int files_transaction_prepare(struct ref_store *ref_store,
                         */
                        if (!packed_transaction) {
                                packed_transaction = ref_store_transaction_begin(
-                                               refs->packed_ref_store, 0, err);
+                                               refs->packed_ref_store,
+                                               REF_TRANSACTION_SKIP_HOOK, err);
                                if (!packed_transaction) {
                                        ret = TRANSACTION_GENERIC_ERROR;
                                        goto cleanup;
@@ -3047,7 +3049,8 @@ static int files_initial_transaction_commit(struct ref_store *ref_store,
                                 &affected_refnames))
                BUG("initial ref transaction called with existing refs");
 
-       packed_transaction = ref_store_transaction_begin(refs->packed_ref_store, 0, err);
+       packed_transaction = ref_store_transaction_begin(refs->packed_ref_store,
+                                                        REF_TRANSACTION_SKIP_HOOK, err);
        if (!packed_transaction) {
                ret = TRANSACTION_GENERIC_ERROR;
                goto cleanup;

diff --git a/t/t1416-ref-transaction-hooks.sh b/t/t1416-ref-transaction-hooks.sh
index f9d3d5213f8992860062aea1431170d1264f496d..4e1e84a91f365b1a625273a552a87ddb937be1b6 100755 (executable)
--- a/t/t1416-ref-transaction-hooks.sh
+++ b/t/t1416-ref-transaction-hooks.sh
@@ -175,16 +175,11 @@ test_expect_success 'deleting packed ref calls hook once' '
        git update-ref -d refs/heads/to-be-deleted $POST_OID &&
 
        # We only expect a single hook invocation, which is the logical
-       # deletion. But currently, we see two interleaving transactions, once
-       # for deleting the loose refs and once for deleting the packed ref.
+       # deletion.
        cat >expect <<-EOF &&
-               prepared
-               $ZERO_OID $ZERO_OID refs/heads/to-be-deleted
                prepared
                $POST_OID $ZERO_OID refs/heads/to-be-deleted
                committed
-               $ZERO_OID $ZERO_OID refs/heads/to-be-deleted
-               committed
                $POST_OID $ZERO_OID refs/heads/to-be-deleted
        EOF