storageutil: extract copy metadata retrieval out of filelog
As part of implementing an alternate storage backend, I found myself
reinventing this wheel.
Let's create a utility function for doing the work.
Differential Revision: https://phab.mercurial-scm.org/D4800
@echo off
powershell -NoProfile -ExecutionPolicy unrestricted -Command "& '%~dp0\editmergeps.ps1' %*"