hooks: remove implicit dependency on the_repository

We implicitly depend on `the_repository` in our hook subsystem because
we use `strbuf_git_path()` to compute hook paths. Remove this dependency
by accepting a `struct repository` as parameter instead.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

reset.c

@@ -79,7 +79,7 @@ static int update_refs(const struct reset_head_opts *opts,
 						 reflog_head);
 	}
 	if (!ret && run_hook)
-		run_hooks_l("post-checkout",
+		run_hooks_l(the_repository, "post-checkout",
 			    oid_to_hex(head ? head : null_oid()),
 			    oid_to_hex(oid), "1", NULL);
 	strbuf_release(&msg);