Merge branch 'ab/diff-deferred-free'

A small memleak in "diff -I<regexp>" has been corrected.

* ab/diff-deferred-free:
  diff: plug memory leak from regcomp() on {log,diff} -I
  diff: add an API for deferred freeing

diff --cc builtin/log.c
Simple merge

diff --cc log-tree.c
Simple merge