shallowutil: introduce a helper function isenabled() This patch introduces a inenabled() function which will check whether remotefilelog is enabled or not. The function is then also used at all the places where check whether remotefilelog is enabled or not. The new function makes code easy to read without need to understand what is the constant involved and why we are checking repo.requirements. Differential Revision: https://phab.mercurial-scm.org/D5190