get_main_ref_store: BUG() when outside a repository

If we don't have a repository, then we can't initialize the
ref store.  Prior to 64a741619d (refs: store the main ref
store inside the repository struct, 2018-04-11), we'd try to
access get_git_dir(), and outside a repository that would
trigger a BUG(). After that commit, though, we directly use
the_repository->git_dir; if it's NULL we'll just segfault.

Let's catch this case and restore the BUG() behavior.
Obviously we don't ever want to hit this code, but a BUG()
is a lot more helpful than a segfault if we do.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/refs.c b/refs.c
index 9b56fa9b81..4a44e44b6a 100644
--- a/refs.c
+++ b/refs.c
@@ -1654,6 +1654,9 @@ struct ref_store *get_main_ref_store(struct repository *r)
 	if (r->refs)
 		return r->refs;
 
+	if (!r->gitdir)
+		BUG("attempting to get main_ref_store outside of repository");
+
 	r->refs = ref_store_init(r->gitdir, REF_STORE_ALL_CAPS);
 	return r->refs;
 }