D388: filemerge: extract _maketemp and _makebackup

[phillco (Phil Cohen)]

phillco added a comment.


  (Fixed trailing space)

REPOSITORY
  rHG Mercurial

REVISION DETAIL
  https://phab.mercurial-scm.org/D388

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