Subject: [PATCH 5/4] apply: fix uninitialized hash function

From: Junio C Hamano <[email-masked]>
Date: Mon, 13 May 2024 14:28:27 -0700

"git apply" can work outside a repository as a better "GNU patch",
but when it does so, it still assumed that it can access
the_hash_algo, which is no longer true in the new world order.

Make sure we explicitly fall back to SHA-1 algorithm for backward
compatibility.  Just like we argued for hash-objects, we probably
should have a mechanism to specify the hash algorithm used outside
a repository.

Signed-off-by: Junio C Hamano <[email-masked]>
---

 * After finishing these steps, it started to dawn on me that we
   probably can instead add GIT_DEFAULT_HASH_ALGO environment
   variable for exactly that purpose.  Then the escape hatch I
   introduced in [1/4] can become just that.

 builtin/apply.c         | 4 ++++
 t/t1517-outside-repo.sh | 2 +-
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/builtin/apply.c b/builtin/apply.c
index 861a01910c..e9175f820f 100644
--- a/builtin/apply.c
+++ b/builtin/apply.c
@@ -1,6 +1,7 @@
 #include "builtin.h"
 #include "gettext.h"
 #include "repository.h"
+#include "hash.h"
 #include "apply.h"
 
 static const char * const apply_usage[] = {
@@ -18,6 +19,9 @@ int cmd_apply(int argc, const char **argv, const char *prefix)
 	if (init_apply_state(&state, the_repository, prefix))
 		exit(128);
 
+	if (!the_hash_algo)
+		repo_set_hash_algo(the_repository, GIT_HASH_SHA1);
+
 	argc = apply_parse_options(argc, argv,
 				   &state, &force_apply, &options,
 				   apply_usage);
diff --git a/t/t1517-outside-repo.sh b/t/t1517-outside-repo.sh
index 854bb8f343..6f32a40c6d 100755
--- a/t/t1517-outside-repo.sh
+++ b/t/t1517-outside-repo.sh
@@ -39,7 +39,7 @@ test_expect_success 'hash-object outside repository' '
 	test_cmp hash.expect hash.actual
 '
 
-test_expect_failure 'apply a patch outside repository' '
+test_expect_success 'apply a patch outside repository' '
 	(
 		cd non-repo &&
 		cp ../nums.old nums &&
-- 
2.45.0-145-g3e4a232f6e