refs: implement releasing ref storages

Ref storages are typically only initialized once for `the_repository`
and then never released. Until now we got away with that without causing
memory leaks because `the_repository` stays reachable, and because the
ref backend is reachable via `the_repository` its memory basically never
leaks.

This is about to change though because of the upcoming migration logic,
which will create a secondary ref storage. In that case, we will either
have to release the old or new ref storage to avoid leaks.

Implement a new `release` callback and expose it via a new
`ref_storage_release()` function.

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

1 files changed, 5 insertions, 0 deletions

diff --git a/refs.h b/refs.h
index 421ff9fdb7..b11c250e8a 100644
--- a/refs.h
+++ b/refs.h
@@ -119,6 +119,11 @@ int is_branch(const char *refname);
 int ref_store_create_on_disk(struct ref_store *refs, int flags, struct strbuf *err);
 
 /*
+ * Release all memory and resources associated with the ref store.
+ */
+void ref_store_release(struct ref_store *ref_store);
+
+/*
  * Return the peeled value of the oid currently being iterated via
  * for_each_ref(), etc. This is equivalent to calling:
  *