manifest: add getstorage() to manifestlog and use it globally It is a common pattern to obtain a directory manifest storage instance (a manifestrevlog) by going through manifestlog._revlog.dirlog(). Why access to storage and caching of other manifests is done through manifestrevlog instead of manifestlog, I don't know. This commit establishes a getstorage(tree) API on manifestlog and imanifestlog that provides a public API for accessing manifest storage. All consumers previously using private attributes have been updated to use this new method. .. api:: manifestlog now has a getstorage(tree) method It should be used for obtaining an object representing the manifest's storage implementation. Accessing manifestlog._revlog should be avoided. Differential Revision: https://phab.mercurial-scm.org/D4277