Merge branch 'tg/stash-untracked-with-pathspec-fix'

"git stash push -u -- <pathspec>" gave an unnecessary and confusing
error message when there was no tracked files that match the
<pathspec>, which has been fixed.

* tg/stash-untracked-with-pathspec-fix:
stash: drop superfluos pathspec parameter
stash push -u: don't create empty stash
stash push: avoid printing errors
stash: fix nonsense pipeline

diff --cc git-stash.sh
Simple merge