Merge branch 'jc/diffcore-rotate'

"git {diff,log} --{skip,rotate}-to=<path>" allows the user to
discard diff output for early paths or move them to the end of the
output.

* jc/diffcore-rotate:
  diff: --{rotate,skip}-to=<path>

diff --cc builtin/diff-files.c
Simple merge

diff --cc builtin/diff-index.c
Simple merge

diff --cc builtin/diff-tree.c
Simple merge

diff --cc builtin/diff.c
Simple merge

diff --cc diff.c
Simple merge

diff --cc diff.h
Simple merge