packed-backend: check whether the "packed-refs" is regular

Although "git-fsck(1)" and "packed-backend.c" will check some
consistency and correctness of "packed-refs" file, they never check the
filetype of the "packed-refs". The user should always use "git
packed-refs" command to create the raw regular "packed-refs" file, so we
need to explicitly check this in "git refs verify".

Use "lstat" to check the file mode. If we cannot check the file status,
this is OK because there is a chance that there is no "packed-refs" in
the repo.

Reuse "FSCK_MSG_BAD_REF_FILETYPE" fsck message id to report the error to
the user if "packed-refs" is not a regular file.

Mentored-by: Patrick Steinhardt <[email protected]>
Mentored-by: Karthik Nayak <[email protected]>
Signed-off-by: shejialuo <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: shejialuo

refs/packed-backend.c

@@ -5,6 +5,7 @@
 #include "../config.h"
 #include "../dir.h"
 #include "../gettext.h"
+#include "../fsck.h"
 #include "../hash.h"
 #include "../hex.h"
 #include "../refs.h"
@@ -1748,15 +1749,39 @@ static struct ref_iterator *packed_reflog_iterator_begin(struct ref_store *ref_s
 	return empty_ref_iterator_begin();
 }
 
-static int packed_fsck(struct ref_store *ref_store UNUSED,
-		       struct fsck_options *o UNUSED,
+static int packed_fsck(struct ref_store *ref_store,
+		       struct fsck_options *o,
 		       struct worktree *wt)
 {
+	struct packed_ref_store *refs = packed_downcast(ref_store,
+							REF_STORE_READ, "fsck");
+	struct stat st;
+	int ret = 0;
 
 	if (!is_main_worktree(wt))
-		return 0;
+		goto cleanup;
 
-	return 0;
+	/*
+	 * If the packed-refs file doesn't exist, there's nothing to
+	 * check.
+	 */
+	if (lstat(refs->path, &st) < 0)
+		goto cleanup;
+
+	if (o->verbose)
+		fprintf_ln(stderr, "Checking packed-refs file %s", refs->path);
+
+	if (!S_ISREG(st.st_mode)) {
+		struct fsck_ref_report report = { 0 };
+		report.path = "packed-refs";
+
+		ret = fsck_report_ref(o, &report, FSCK_MSG_BAD_REF_FILETYPE,
+				      "not a regular file");
+		goto cleanup;
+	}
+
+cleanup:
+	return ret;
 }
 
 struct ref_storage_be refs_be_packed = {

t/t0602-reffiles-fsck.sh

@@ -626,4 +626,24 @@ test_expect_success 'ref content checks should work with worktrees' '
 	test_cmp expect err
 '
 
+test_expect_success SYMLINKS 'the filetype of packed-refs should be checked' '
+	test_when_finished "rm -rf repo" &&
+	git init repo &&
+	cd repo &&
+	test_commit default &&
+	git branch branch-1 &&
+	git branch branch-2 &&
+	git branch branch-3 &&
+	git pack-refs --all &&
+
+	mv .git/packed-refs .git/packed-refs-back &&
+	ln -sf packed-refs-bak .git/packed-refs &&
+	test_must_fail git refs verify 2>err &&
+	cat >expect <<-EOF &&
+	error: packed-refs: badRefFiletype: not a regular file
+	EOF
+	rm .git/packed-refs &&
+	test_cmp expect err
+'
+
 test_done