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

[yuja (Yuya Nishihara)]

yuja added inline comments.

INLINE COMMENTS

> cmdutil.py:344
>                  reviewedpatch = ui.edit(patchtext, "",
> -                                        extra={"suffix": ".diff"},
> +                                        action="diff",
>                                          repopath=repo.path)

Sorry for late review, but doesn't it change the suffix from
`.diff` to `.diff.hg.txt`?

REPOSITORY
  rHG Mercurial

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

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