narrow: add test showing that local-to-local narrow clones don't work
It turns out they've never actually worked: prior to some recent
refactoring they just unintentionally followed the full-clone path,
which we unintentionally relied on in a test at Google.
Differential Revision: https://phab.mercurial-scm.org/D4640
@echo off
powershell -NoProfile -ExecutionPolicy unrestricted -Command "& '%~dp0\editmergeps.ps1' %*"