D399: filemerge: eliminate most uses of tempfiles

[phillco (Phil Cohen)]

phillco added a comment.


  Fixed, thanks @lothiraldan :)

REPOSITORY
  rHG Mercurial

REVISION DETAIL
  https://phab.mercurial-scm.org/D399

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