bundle verify: error out if called without an object database

The deal with bundles is: they really are thin packs, with very little
sugar on top. So we really need a repository (or more appropriately, an
object database) to work with, when asked to verify a bundle.

Let's error out with a useful error message if `git bundle verify` is
called without such an object database to work with.

Reported by Konstantin Ryabitsev.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

bundle.c

@@ -142,6 +142,9 @@ int verify_bundle(struct repository *r,
 	int i, ret = 0, req_nr;
 	const char *message = _("Repository lacks these prerequisite commits:");
 
+	if (!r || !r->objects || !r->objects->odb)
+		return error(_("need a repository to verify a bundle"));
+
 	repo_init_revisions(r, &revs, NULL);
 	for (i = 0; i < p->nr; i++) {
 		struct ref_list_entry *e = p->list + i;

t/t5607-clone-bundle.sh

@@ -14,6 +14,12 @@ test_expect_success 'setup' '
 	git tag -d third
 '
 
+test_expect_success '"verify" needs a worktree' '
+	git bundle create tip.bundle -1 master &&
+	test_must_fail nongit git bundle verify ../tip.bundle 2>err &&
+	test_i18ngrep "need a repository" err
+'
+
 test_expect_success 'annotated tags can be excluded by rev-list options' '
 	git bundle create bundle --all --since=7.Apr.2005.15:14:00.-0700 &&
 	git ls-remote bundle > output &&