Merge branch 'ms/mailmap'

* ms/mailmap:
  Move mailmap documentation into separate file
  Change current mailmap usage to do matching on both name and email of author/committer.
  Add map_user() and clear_mailmap() to mailmap
  Add find_insert_index, insert_at_index and clear_func functions to string_list
  Add mailmap.file as configurational option for mailmap location

diff --cc Documentation/config.txt
Simple merge

diff --cc builtin-blame.c
Simple merge

diff --cc cache.h
Simple merge

diff --cc pretty.c
Simple merge