stash: allow stashes to be referenced by index only
Instead of referencing "stash@{n}" explicitly, make it possible to
simply reference as "n". Most users only reference stashes by their
position in the stash stack (what I refer to as the "index" here).
The syntax for the typical stash (stash@{n}) is slightly annoying and
easy to forget, and sometimes difficult to escape properly in a
script. Because of this the capability to do things with the stash by
simply referencing the index is desirable.
This patch includes the superior implementation provided by Ă˜sse Walle
(thanks for that), with a slight change to fix a broken test in the test
suite. I also merged the test scripts as suggested by Jeff King, and
un-wrapped the documentation as suggested by Junio Hamano.
Signed-off-by: Aaron M Watson <watsona4@gmail.com> Reviewed-by: Jeff King <peff@peff.net>