Tag value handling for governance repo with note

- Do not use "to-be-released" value used for election
  rendering page to refer to projects.yaml file on governance
  repo. Instead, render the link on the master branch.
- Document the purpose of the tag value on README

Change-Id: I8d6c72ccd0abf11131a98619f73de7b800935004

README.rst

@@ -36,6 +36,12 @@ As early as possible but at least a month before election starts:
 
   * ``edit configuration.yaml``
 
+  .. note::
+
+     ``to-be-released`` tag value is used during the election process.
+     After the election is over, the tag value is updated
+     for ``openstack/governance`` repository.
+
 * Prepare new election, e.g.:
 
   * ``tox -evenv -- create-directories``

doc/source/_exts/configuration.jinja

@@ -1,4 +1,8 @@
 .. |Timeframe| replace:: {{ timeframe['name'] }} timeframe ({{ timeframe['start_str'] }} to {{ timeframe['end_str'] }})
 .. |PreferredEmailDeadLine| replace:: {{ timeframe['email_deadline_str'] }}
+{% if tag == 'to-be-released' %}
+.. |Projects.yaml| replace:: https://opendev.org/openstack/governance/src/branch/master/reference/projects.yaml
+{% else %}
 .. |Projects.yaml| replace:: https://opendev.org/openstack/governance/src/tag/{{ tag }}/reference/projects.yaml
-.. |TCSeats| replace:: {{ tc_seats }}
+{% endif %}
+.. |TCSeats| replace:: {{ tc_seats }}