localrepo: validate supported requirements in makelocalrepository() This should be a glorified code move. I did take the opportunity to refactor things. We now have a separate function for gathering requirements and one for validating them. I also mode cosmetic changes to the code, such as not using abbreviations and using a set instead of list to model missing requirements. Differential Revision: https://phab.mercurial-scm.org/D4569