Merge branch 'rs/add-patch-quit'

The 'q'(uit) command in "git add -p" has been improved to quit
without doing any meaningless work before leaving, and giving EOF
(typically control-D) to the prompt is made to behave the same way.

* rs/add-patch-quit:
  add-patch: quit on EOF
  add-patch: quit without skipping undecided hunks