D674: filemerge: use arbitraryfilectx for backup files

[phillco (Phil Cohen)]

phillco added inline comments.

INLINE COMMENTS

> martinvonz wrote in filemerge.py:744
> Can we not simply make arbitraryfilectx.cmp() something like
> 
>   def cmp(self, fctx):
>       if isinstance(fctx, arbitraryfilectx):
>           return filecmp.cmp(self.path(), fctx.path())
>       return self.data() != otherfilectx.data()

`fcd` is a `workingfilectx`, so it'd need to need to be something like:

  return filecmp.cmp(self.path(), self._repo.wjoin(fctx.path()))

and `arbitraryfilectx` doesn't have a `_repo` because we use it in `contrib/simplemerge`. Maybe we could make it an optional property and raise in this case if it's missing? `contrib/simplemerge` doesn't need it.

REPOSITORY
  rHG Mercurial

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

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