D674: filemerge: use arbitraryfilectx for backup files

[phillco (Phil Cohen)]

phillco abandoned this revision.
phillco added a comment.


  I've split this into https://phab.mercurial-scm.org/D1056, https://phab.mercurial-scm.org/D1057, https://phab.mercurial-scm.org/D1058, https://phab.mercurial-scm.org/D1059, https://phab.mercurial-scm.org/D1060, so abandoning this version.
  
  @martinvonz

REPOSITORY
  rHG Mercurial

REVISION DETAIL
  https://phab.mercurial-scm.org/D674

To: phillco, #hg-reviewers, martinvonz
Cc: sid0, martinvonz, mercurial-devel