localrepo: add repository feature when repo can be stream cloned Right now, the wire protocol server assumes all repository objects can be stream cloned (unless the stream clone feature is disabled via config option). But not all storage backends or repository objects may support stream clone. This commit defines a repository feature denoting whether stream clone is supported. The feature is defined for revlog-based repositories, which should currently be "all repositories." Differential Revision: https://phab.mercurial-scm.org/D4852