diff -r 05264fc9d8d6 -r f257943e47ab mercurial/repository.py
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mercurial/repository.py	Sun Aug 13 10:58:48 2017 -0700
@@ -0,0 +1,71 @@
+# repository.py - Interfaces and base classes for repositories and peers.
+#
+# Copyright 2017 Gregory Szorc <gregory.szorc@gmail.com>
+#
+# This software may be used and distributed according to the terms of the
+# GNU General Public License version 2 or any later version.
+
+from __future__ import absolute_import
+
+import abc
+
+class _basepeer(object):
+    """Represents a "connection" to a repository.
+
+    This is the base interface for representing a connection to a repository.
+    It holds basic properties and methods applicable to all peer types.
+
+    This is not a complete interface definition and should not be used
+    outside of this module.
+    """
+    __metaclass__ = abc.ABCMeta
+
+    @abc.abstractproperty
+    def ui(self):
+        """ui.ui instance."""
+
+    @abc.abstractmethod
+    def url(self):
+        """Returns a URL string representing this peer.
+
+        Currently, implementations expose the raw URL used to construct the
+        instance. It may contain credentials as part of the URL. The
+        expectations of the value aren't well-defined and this could lead to
+        data leakage.
+
+        TODO audit/clean consumers and more clearly define the contents of this
+        value.
+        """
+
+    @abc.abstractmethod
+    def local(self):
+        """Returns a local repository instance.
+
+        If the peer represents a local repository, returns an object that
+        can be used to interface with it. Otherwise returns ``None``.
+        """
+
+    @abc.abstractmethod
+    def peer(self):
+        """Returns an object conforming to this interface.
+
+        Most implementations will ``return self``.
+        """
+
+    @abc.abstractmethod
+    def canpush(self):
+        """Returns a boolean indicating if this peer can be pushed to."""
+
+    @abc.abstractmethod
+    def close(self):
+        """Close the connection to this peer.
+
+        This is called when the peer will no longer be used. Resources
+        associated with the peer should be cleaned up.
+        """
+
+class peer(_basepeer):
+    """Unified interface and base class for peer repositories.
+
+    All peer instances must inherit from this class.
+    """