Subject: [PATCH] object-file: don't use object database without a repository

From: Luca Stefani <[email-masked]>
Date: Sat, 4 Apr 2026 19:28:17 +0200

When running `git diff -- $file1 $file2' on large enough files,
index_fd() attempts to use 'the_repository->objects', assuming it
is initialized, but that's not the case for non-repository usecases.

When git diff is invoked without a backing repository,
INDEX_WRITE_OBJECT is never set in flags, meaning only the hash is
needed and nothing should be written to the object store.

Enforce the use of index_core() in this case.

Signed-off-by: Luca Stefani <[email-masked]>
---
 object-file.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/object-file.c b/object-file.c
index f0b029ff0b..68303aa99c 100644
--- a/object-file.c
+++ b/object-file.c
@@ -1654,7 +1654,8 @@ int index_fd(struct index_state *istate, struct object_id *oid,
 	} else if ((st->st_size >= 0 &&
 		    (size_t)st->st_size <= repo_settings_get_big_file_threshold(istate->repo)) ||
 		   type != OBJ_BLOB ||
-		   (path && would_convert_to_git(istate, path))) {
+		   (path && would_convert_to_git(istate, path)) ||
+		   !(flags & INDEX_WRITE_OBJECT)) {
 		ret = index_core(istate, oid, fd, xsize_t(st->st_size),
 				 type, path, flags);
 	} else {
-- 
2.54.0.rc0.dirty