Merge branch 'vs/complete-stash-show-p-fix'

The command line completion script (in contrib/) tried to complete
"git stash -p" as if it were "git stash push -p", but it was too
aggressive and also affected "git stash show -p", which has been
corrected.

* vs/complete-stash-show-p-fix:
  completion: don't override given stash subcommand with -p

diff --cc contrib/completion/git-completion.bash
Simple merge