Add canonical hostname to source object

This is the start of the implementation of:
http://lists.openstack.org/pipermail/openstack-infra/2017-March/005208.html

It lets us associate a canonical hostname with every connection
that we will later use to uniquely identify source code repos.

Story: 2000953
Change-Id: I7f2e64944d46f304e63a54078e682fd5e1682f27
diff --git a/doc/source/connections.rst b/doc/source/connections.rst
index 298100a..614b44a 100644
--- a/doc/source/connections.rst
+++ b/doc/source/connections.rst
@@ -22,6 +22,13 @@
   FQDN of Gerrit server.
   ``server=review.example.com``
 
+**canonical_hostname**
+  The canonical hostname associated with the git repos on the Gerrit
+  server.  Defaults to the value of **server**.  This is used to
+  identify repos from this connection by name and in preparing repos
+  on the filesystem for use by jobs.
+  ``canonical_hostname=git.example.com``
+
 **port**
   Optional: Gerrit server port.
   ``port=29418``