contrib/editmergeps.bat

largefiles: take lock before writing requirements

With `share-safe`, we will also write file in the store. We now take the `lock`
as needed.

Differential Revision: https://phab.mercurial-scm.org/D11992

@echo off
powershell -NoProfile -ExecutionPolicy unrestricted -Command "& '%~dp0\editmergeps.ps1' %*"