mergestate: split out merge state handling code from main merge module
There's already some pretty reasonable encapsulation here, but I want
to make the mergestate storage a property of the context so memctx
instances can do a reasonable thing. This is the first step in a
reshuffle to make that easier.
Differential Revision: https://phab.mercurial-scm.org/D8550
== New Features ==
== New Experimental Features ==
== Backwards Compatibility Changes ==
== Internal API Changes ==
* logcmdutil.diffordiffstat() now takes contexts instead of nodes.
* The `mergestate` class along with some related methods and constants have
moved from `mercurial.merge` to a new `mercurial.mergestate` module.