prune_ref(): call `ref_transaction_add_update()` directly

`prune_ref()` needs to use the `REF_ISPRUNING` flag, but we want to
make that flag private to the files backend. So instead of calling
`ref_transaction_delete()`, which is a public function and therefore
shouldn't allow the `REF_ISPRUNING` flag, change `prune_ref()` to call
`ref_transaction_add_update()`, which is private to the refs
module. (Note that we don't need any of the other services provided by
`ref_transaction_delete()`.)

This allows us to change `ref_transaction_update()` to reject the
`REF_ISPRUNING` flag. Do so by adjusting
`REF_TRANSACTION_UPDATE_ALLOWED_FLAGS`. Also add parentheses to its
definition to avoid potential future mishaps.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

2 files changed, 17 insertions, 12 deletions

diff --git a/refs.h b/refs.h
index 15fd419c7d..4ffef9502d 100644
--- a/refs.h
+++ b/refs.h
@@ -349,9 +349,7 @@ int refs_pack_refs(struct ref_store *refs, unsigned int flags);
  * Flags that can be passed in to ref_transaction_update
  */
 #define REF_TRANSACTION_UPDATE_ALLOWED_FLAGS \
-	REF_ISPRUNING |                      \
-	REF_FORCE_CREATE_REFLOG |            \
-	REF_NODEREF
+	(REF_NODEREF | REF_FORCE_CREATE_REFLOG)
 
 /*
  * Setup reflog before using. Fill in err and return -1 on failure.
diff --git a/refs/files-backend.c b/refs/files-backend.c
index fadf1036d3..ba72d28b13 100644
--- a/refs/files-backend.c
+++ b/refs/files-backend.c
@@ -989,22 +989,29 @@ static void prune_ref(struct files_ref_store *refs, struct ref_to_prune *r)
 {
 	struct ref_transaction *transaction;
 	struct strbuf err = STRBUF_INIT;
+	int ret = -1;
 
 	if (check_refname_format(r->name, 0))
 		return;
 
 	transaction = ref_store_transaction_begin(&refs->base, &err);
-	if (!transaction ||
-	    ref_transaction_delete(transaction, r->name, &r->oid,
-				   REF_ISPRUNING | REF_NODEREF, NULL, &err) ||
-	    ref_transaction_commit(transaction, &err)) {
-		ref_transaction_free(transaction);
+	if (!transaction)
+		goto cleanup;
+	ref_transaction_add_update(
+			transaction, r->name,
+			REF_NODEREF | REF_HAVE_NEW | REF_HAVE_OLD | REF_ISPRUNING,
+			&null_oid, &r->oid, NULL);
+	if (ref_transaction_commit(transaction, &err))
+		goto cleanup;
+
+	ret = 0;
+
+cleanup:
+	if (ret)
 		error("%s", err.buf);
-		strbuf_release(&err);
-		return;
-	}
-	ref_transaction_free(transaction);
 	strbuf_release(&err);
+	ref_transaction_free(transaction);
+	return;
 }
 
 /*