D464: editor: use an unambiguous path suffix for editor files

[mbolin (Michael Bolin)]

mbolin added a comment.


  @ryanmce I'm happy to write a test, but what do you want me to target: `ui.edit()` itself?

REPOSITORY
  rHG Mercurial

REVISION DETAIL
  https://phab.mercurial-scm.org/D464

To: mbolin, quark, durin42, #hg-reviewers, ryanmce
Cc: smf, ryanmce, mercurial-devel