[PATCH v3] multi-pack-index: fix *.rev cleanups with --object-dir

[Johannes Berg <johannes@xxxxxxxxxxxxxxxx>]

If using --object-dir to point into a repo while the current
working dir is outside, such as

  git init /repo
  git -C /repo ... # add some objects
  cd /non-repo
  git multi-pack-index --object-dir /repo/.git/objects/ write

the binary will segfault trying to access the object-dir via
the repo it found, but that's not fully initialized. Fix it
to use the object_dir properly to clean up the *.rev files,
this avoids the crash and cleans up the *.rev files for the
now rewritten multi-pack-index properly.

Fixes: 38ff7cabb6b8 ("pack-revindex: write multi-pack reverse indexes")
Cc: Taylor Blau <me@xxxxxxxxxxxx>
Signed-off-by: Johannes Berg <johannes@xxxxxxxxxxxxxxxx>
---
v3:
 - use nongit
---
 midx.c                      | 10 +++++-----
 t/t5319-multi-pack-index.sh | 15 +++++++++++++++
 2 files changed, 20 insertions(+), 5 deletions(-)

diff --git a/midx.c b/midx.c
index 321c6fdd2f18..902e1a7a7d9d 100644
--- a/midx.c
+++ b/midx.c
@@ -882,7 +882,7 @@ static void write_midx_reverse_index(char *midx_name, unsigned char *midx_hash,
 	strbuf_release(&buf);
 }
 
-static void clear_midx_files_ext(struct repository *r, const char *ext,
+static void clear_midx_files_ext(const char *object_dir, const char *ext,
 				 unsigned char *keep_hash);
 
 static int midx_checksum_valid(struct multi_pack_index *m)
@@ -1086,7 +1086,7 @@ static int write_midx_internal(const char *object_dir, struct multi_pack_index *
 
 	if (flags & MIDX_WRITE_REV_INDEX)
 		write_midx_reverse_index(midx_name, midx_hash, &ctx);
-	clear_midx_files_ext(the_repository, ".rev", midx_hash);
+	clear_midx_files_ext(object_dir, ".rev", midx_hash);
 
 	commit_lock_file(&lk);
 
@@ -1135,7 +1135,7 @@ static void clear_midx_file_ext(const char *full_path, size_t full_path_len,
 		die_errno(_("failed to remove %s"), full_path);
 }
 
-static void clear_midx_files_ext(struct repository *r, const char *ext,
+static void clear_midx_files_ext(const char *object_dir, const char *ext,
 				 unsigned char *keep_hash)
 {
 	struct clear_midx_data data;
@@ -1146,7 +1146,7 @@ static void clear_midx_files_ext(struct repository *r, const char *ext,
 				    hash_to_hex(keep_hash), ext);
 	data.ext = ext;
 
-	for_each_file_in_pack_dir(r->objects->odb->path,
+	for_each_file_in_pack_dir(object_dir,
 				  clear_midx_file_ext,
 				  &data);
 
@@ -1165,7 +1165,7 @@ void clear_midx_file(struct repository *r)
 	if (remove_path(midx))
 		die(_("failed to clear multi-pack-index at %s"), midx);
 
-	clear_midx_files_ext(r, ".rev", NULL);
+	clear_midx_files_ext(r->objects->odb->path, ".rev", NULL);
 
 	free(midx);
 }
diff --git a/t/t5319-multi-pack-index.sh b/t/t5319-multi-pack-index.sh
index 3d4d9f10c31b..665c6d64a0ab 100755
--- a/t/t5319-multi-pack-index.sh
+++ b/t/t5319-multi-pack-index.sh
@@ -201,6 +201,21 @@ test_expect_success 'write midx with twelve packs' '
 
 compare_results_with_midx "twelve packs"
 
+test_expect_success 'multi-pack-index *.rev cleanup with --object-dir' '
+	git init objdir-test-repo &&
+	test_when_finished "rm -rf objdir-test-repo" &&
+	(
+		cd objdir-test-repo &&
+		test_commit base &&
+		git repack -d
+	) &&
+	rev="objdir-test-repo/$objdir/pack/multi-pack-index-abcdef123456.rev" &&
+	touch $rev &&
+	nongit git multi-pack-index --object-dir="$(pwd)/objdir-test-repo/$objdir" write &&
+	test_path_is_file objdir-test-repo/$objdir/pack/multi-pack-index &&
+	test_path_is_missing $rev
+'
+
 test_expect_success 'warn on improper hash version' '
 	git init --object-format=sha1 sha1 &&
 	(
-- 
2.31.1