tests/test-config-case.t

diff: move b85diff to mdiff module

b85diff generates a binary diff, so we move this code to mdiff module
along with unidiff for text diffs. All diffing mechanisms will be in the
same place.

In an upcoming patch we will remove the responsibility to print the
index header from b85diff and move it back to patch, since it's
a patch metadata header, not part of the diff generation.

hide outer repo
  $ hg init

  $ echo '[Section]' >> $HGRCPATH
  $ echo 'KeY = Case Sensitive' >> $HGRCPATH
  $ echo 'key = lower case' >> $HGRCPATH

  $ hg showconfig Section
  Section.KeY=Case Sensitive
  Section.key=lower case