Merge branch 'nk/stash-show-config'

Users who are too busy to type three extra keystrokes to ask for
"git stash show -p" can now set stash.showPatch configuration
varible to true to always see the actual patch, not just the list
of paths affected with feel for the extent of damage via diffstat.

* nk/stash-show-config:
  stash: allow "stash show" diff output configurable

diff --cc Documentation/config.txt
Simple merge

diff --cc git-stash.sh
Simple merge