Merge branch 'jh/dirstat' into maint

* jh/dirstat:
--dirstat: In case of renames, use target filename instead of source filename
Teach --dirstat not to completely ignore rearranged lines within a file
--dirstat-by-file: Make it faster and more correct
--dirstat: Describe non-obvious differences relative to --stat or regular diff

diff --cc diff.c
Simple merge