filemerge: use arbitraryfilectx for backups With in-memory merge, backup files might be overlayworkingfilectxs stored in memory. But they could also be real files if the user's backup directory is outside the working dir. Rather than have two code paths everywhere, let's use arbitraryfilectx so they can be consistent. Differential Revision: https://phab.mercurial-scm.org/D1057

registrar: add support for storing the type of command in func object This patch adds support for storing the type of command which is going to run in the func object. For this it does the following: 1) Add three possible values as attributes to the registrar.command class 2) Add a new argument to registrar.command._doregister function 3) Add a new attribute cmdtype to the func object The type of command will be helpful in deciding what level of access on hidden commits it can has. Differential Revision: https://phab.mercurial-scm.org/D736