Merge branch 'jc/pickaxe-grep' into next

* jc/pickaxe-grep:
  diff/log -G<pattern>: tests
  git log/diff: add -G<regexp> that greps in the patch text
  diff: pass the entire diff-options to diffcore_pickaxe()
  gitdiffcore doc: update pickaxe description

diff --cc diff.c
Simple merge