Merge branch 'jc/diff-stat'

* jc/diff-stat:
  diff --stat: ensure at least one '-' for deletions, and one '+' for additions
  diff --stat=width[,name-width]: allow custom diffstat output width.
  diff --stat: color output.
  diff --stat: allow custom diffstat output width.

diff --cc diff.c
Simple merge

diff --cc diff.h
Simple merge