Summary:
The root issue is described in the new ``workingflags()`` function -- ``workingfilectx.flags()`` ought to read from the working copy, but instead reads from the working copy's p1.
Rather than force a big rewrite to adapt all the old code (which might be a waste if we end up rewriting the context classes), let's add a new function with the behavior we want, and callers can detect for it and call it.
simplemerge is the only callsite that needs this behavior, AFAICT.
Previous attempt: D6694292
Reviewed By: singhsrb
Differential Revision: D7083239
fbshipit-source-id: 6f30b877958d40106203e088fe724ab491b541b9
