merge: don't call update hook when using in-memory context...
merge: don't call update hook when using in-memory context
I'm pretty sure many hook implementors will assume that they can
inspect the working copy and/or dirstate parents when the hook is
called, so I don't think we should call the hook when using an
in-memory context. The new behavior matches that of the preupdate
hook.
Differential Revision:
https://phab.mercurial-scm.org/D7898
