localrepo: support shared repo creation Previously, hg.share() had its own logic for creating a new repository on the filesystem. With the recent introduction of the createopts dict for passing options to influence repository creation, it is now possible to consolidate the repo creation code for both the normal and shared use cases. This commit teaches the repo creation code in localrepo to recognize when we're creating a shared repo and to act appropriately. Meaningful behavior should be identical. However, there are a few subtle changes: * The .hg/requires file is written out in sorted order (rather than having share-related requirements appended at end). * The .hg directory is created with notindexed=True when a shared repo is being created. Differential Revision: https://phab.mercurial-scm.org/D4707