D372: simplemerge: add optional context parameters to simplemerge

[phillco (Phil Cohen)]

phillco added inline comments.

INLINE COMMENTS

> martinvonz wrote in simplemerge.py:412
> Seems unfortunate to have both files and contexts. This is what you mentioned today you will replace by use of "arbitraryfilectx"?

They get taken out in https://phab.mercurial-scm.org/D381; they have to co-exist briefly in order to ensure each step of this series can be applied cleanly.

REPOSITORY
  rHG Mercurial

REVISION DETAIL
  https://phab.mercurial-scm.org/D372

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