git-stash: don't complain when listing in a repo with no stash
Previously, the git-log invocation would complain if a repo had not had any stashes created in it yet:
$ git-init $ git-stash fatal: ambiguous argument 'refs/stash': unknown revision or path not in the working tree. Use '--' to separate paths from revisions
Instead, we only call git-log if we actually have a refs/stash. We could alternatively create the ref when any stash command is called, but it's better for the 'list' command to not require write access to the repo.
Signed-off-by: Jeff King <firstname.lastname@example.org> Signed-off-by: Junio C Hamano <email@example.com>