interfaces: create a new folder for interfaces and move repository.py in it I was trying to understand current interfaces and write new ones and I realized we need to improve how current interfaces are organised. This creates a dedicated folder for defining interfaces and move `repository.py` which defines all the current interfaces inside it. Differential Revision: https://phab.mercurial-scm.org/D6741

--- a/contrib/import-checker.py	Thu Aug 22 16:47:31 2019 -0700
+++ b/contrib/import-checker.py	Sun Aug 18 00:45:33 2019 +0300
@@ -28,6 +28,7 @@
     'mercurial.hgweb.common',
     'mercurial.hgweb.request',
     'mercurial.i18n',
+    'mercurial.interfaces',
     'mercurial.node',
     # for revlog to re-export constant to extensions
     'mercurial.revlogutils.constants',