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