[PATCH v2 2/3] branch, tag: retain old OIDs in batched deletions

@@ -16,6 +16,7 @@
 #include "commit.h"
 #include "gettext.h"
 #include "object-name.h"
+#include "oid-array.h"
 #include "remote.h"
 #include "parse-options.h"
 #include "branch.h"

@@ -230,6 +231,7 @@ static int delete_branches(int argc, const char **argv, int force, int kinds,
 	struct strbuf bname = STRBUF_INIT;
 	enum interpret_branch_kind allowed_interpret;
 	struct string_list refs_to_delete = STRING_LIST_INIT_DUP;
+	struct oid_array old_oids = OID_ARRAY_INIT;
 	struct string_list_item *item;
 	int branch_name_pos;
 	const char *fmt_remotes = "refs/remotes/%s";

@@ -314,6 +316,7 @@ static int delete_branches(int argc, const char **argv, int force, int kinds,
 		}
 
 		item = string_list_append(&refs_to_delete, name);
+		oid_array_append(&old_oids, &oid);
 		item->util = xstrdup((flags & REF_ISBROKEN) ? "broken"
 				    : (flags & REF_ISSYMREF) ? target
 				    : repo_find_unique_abbrev(the_repository, &oid, DEFAULT_ABBREV));

@@ -323,7 +326,7 @@ static int delete_branches(int argc, const char **argv, int force, int kinds,
 	}
 
 	if (refs_delete_refs(get_main_ref_store(the_repository), NULL,
-			     &refs_to_delete, NULL, REF_NO_DEREF))
+			     &refs_to_delete, &old_oids, REF_NO_DEREF))
 		ret = 1;
 
 	for_each_string_list_item(item, &refs_to_delete) {

@@ -342,6 +345,7 @@ static int delete_branches(int argc, const char **argv, int force, int kinds,
 		free(describe_ref);
 	}
 	string_list_clear(&refs_to_delete, 0);
+	oid_array_clear(&old_oids);
 
 	free(name);
 	strbuf_release(&bname);

@@ -119,11 +119,14 @@ static int delete_tags(const char **argv)
 {
 	int result;
 	struct string_list refs_to_delete = STRING_LIST_INIT_DUP;
+	struct oid_array old_oids = OID_ARRAY_INIT;
 	struct string_list_item *item;
 
 	result = for_each_tag_name(argv, collect_tags, (void *)&refs_to_delete);
+	for_each_string_list_item(item, &refs_to_delete)
+		oid_array_append(&old_oids, item->util);
 	if (refs_delete_refs(get_main_ref_store(the_repository), NULL,
-			     &refs_to_delete, NULL, REF_NO_DEREF))
+			     &refs_to_delete, &old_oids, REF_NO_DEREF))
 		result = 1;
 
 	for_each_string_list_item(item, &refs_to_delete) {

@@ -137,6 +140,7 @@ static int delete_tags(const char **argv)
 		free(oid);
 	}
 	string_list_clear(&refs_to_delete, 0);
+	oid_array_clear(&old_oids);
 	return result;
 }
 

@@ -14,6 +14,50 @@ test_expect_success setup '
 	POST_OID=$(git rev-parse POST)
 '
 
+test_expect_success 'hook gets old values for batched branch/tag deletion' '
+	test_when_finished "rm -f actual" &&
+	git branch to-delete PRE &&
+	git tag delete-tag POST &&
+	git pack-refs --all &&
+	test_hook reference-transaction <<-\EOF &&
+		if test "$1" = committed
+		then
+			# Ignore backend-internal zero-to-zero records.
+			while read -r old new ref
+			do
+				case "$old" in
+				*[!0]*)
+					echo "$old $new $ref"
+					;;
+				esac
+			done >>actual
+		fi
+	EOF
+	cat >expect <<-EOF &&
+		$PRE_OID $ZERO_OID refs/heads/to-delete
+		$POST_OID $ZERO_OID refs/tags/delete-tag
+	EOF
+	git branch -D to-delete &&
+	git tag -d delete-tag &&
+	test_cmp expect actual
+'
+
+test_expect_success 'branch deletion rejects a concurrent update' '
+	git branch delete-race PRE &&
+	test_hook reference-transaction <<-\EOF &&
+		marker=$(git rev-parse --git-path delete-race-once)
+		if test "$1" = preparing && test ! -e "$marker"
+		then
+			>"$marker"
+			git update-ref refs/heads/delete-race POST
+		fi
+		exit 0
+	EOF
+	test_must_fail git branch -D delete-race 2>err &&
+	test_grep "is at $POST_OID but expected $PRE_OID" err &&
+	test_cmp_rev POST refs/heads/delete-race
+'
+
 test_expect_success 'hook allows updating ref if successful' '
 	git reset --hard PRE &&
 	test_hook reference-transaction <<-\EOF &&