subrepo: add argument to "diff()" to pass "ui" of caller side (issue3712) (API) Color extension achieves colorization by overriding the class of "ui" object just before command execution. Before this patch, "diff()" of abstractsubrepo and classes derived from it has no "ui" argument, so "diff()" of hgsubrepo uses "self._repo.ui" to invoke "cmdutil.diffordiffstat()". For separation of configuration between repositories, revision 573bec4ab7ba changed the initialization source of "self._repo.ui" from "ui"(overridden) to "baseui"(plain) of parent repository. And this caused break of colorization. This patch adds "ui" argument to "diff()" of abstractsubrepo and classes derived from it to pass "ui" object of caller side.

  $ hg init debugrevlog
  $ cd debugrevlog
  $ echo a > a
  $ hg ci -Am adda
  adding a
  $ hg debugrevlog -m
  format : 1
  flags  : inline
  
  revisions     :  1
      merges    :  0 ( 0.00%)
      normal    :  1 (100.00%)
  revisions     :  1
      full      :  1 (100.00%)
      deltas    :  0 ( 0.00%)
  revision size : 44
      full      : 44 (100.00%)
      deltas    :  0 ( 0.00%)
  
  avg chain length  : 0
  compression ratio : 0
  
  uncompressed data size (min/max/avg) : 43 / 43 / 43
  full revision size (min/max/avg)     : 44 / 44 / 44
  delta size (min/max/avg)             : 0 / 0 / 0