Index: README.rst
===================================================================
--- README.rst	(revision 191)
+++ README.rst	(revision 199)
@@ -110,2 +110,37 @@
 __ http://trac.edgewall.org/wiki/0.12/TracRepositoryAdmin#ExplicitSync
 __ http://darcs.net/manual/node7.html#SECTION00712000000000000000
+
+Related repositories
+--------------------
+
+When you manage multiple branches of the same darcs repository, you
+may find useful to inform trac+darcs about that, so that it will show
+additional properties on each changeset:
+
+* a list of other "instances" of the same patch, that is when the
+  changeset is present in other related repositories,
+
+* a list of related repositories where the changeset is *not* present.
+
+To do that, you simply group together the related repositories giving
+them a common ``identity``, an arbitrary string.
+
+You can see current identity of a repository with::
+
+  $ trac-admin . repository identity master
+  No identity set on repository master
+
+and you can set it with::
+
+  $ trac-admin . repository identity master ProjectFoo
+  Identity of repository master set to ProjectFoo
+
+You can adjust it with::
+
+  $ trac-admin . repository identity master ProjectBar
+  Identity of repository master set to ProjectBar (was ProjectFoo)
+
+or remove it::
+
+  $ trac-admin . repository identity master ""
+  Identity removed from repository oldgam