Add some repository documentation

Change https://review.opendev.org/#/c/711827 removes OpenStack specific
content from the OpenDev Manual (previously Infra Manual), move
some OpenStack specific content to a new file in this repo.

This change adds information about project renames and retirements.

Change-Id: I23870f8299dbc2c05568502e39c426de299db4e9

doc/source/index.rst

@@ -20,6 +20,7 @@ Contents:
    open-design
    open-development
    review-the-openstack-way
+   repository
    release-management
    stable-branches
    other-branches

doc/source/repository.rst

@@ -0,0 +1,67 @@
+===================
+Repository Handling
+===================
+
+Project Renames
+===============
+
+If you rename a project to move out from "openstack" namespace to any
+other namespace, follow `this OpenStack TC resolution
+<https://governance.openstack.org/tc/resolutions/20190711-mandatory-repository-retirement.html>`_.
+
+For a project being added to existing official OpenStack project:
+Create an ``openstack/governance`` change and add a "Depends-On:
+project-change-url" of the change you make in the following steps to
+the commit message, and add a comment in the
+``openstack/project-config`` change that references the
+governance change. You will also make sure the PTL has expressed
+approval for the addition in some way.
+
+If you rename an existing official OpenStack project, add the
+``openstack/governance`` change as dependency on the
+``openstack/project-config`` change so that it can merge after the
+rename is done.
+
+The detailed steps for renaming a project are documented in the
+section `Project Renames
+<https://docs.openstack.org/infra/manual/creators.html#project-renames>`_
+of the OpenDev Manual.
+
+Retiring a Repository
+=====================
+
+
+If you need to retire a project and no longer accept patches, it is
+important to communicate that to both users and contributors.  The
+following steps will help you wind down a project gracefully.
+
+.. note::
+
+   The following sections are really separate steps. If your project
+   has jobs set up, you need to submit *four* different changes as
+   explained below and in the OpenDev Manual. We recommend to link
+   these changes with "Depends-On:" and "Needed-By:" headers.
+
+Step 1: Stop requirements syncing (if set up)
+---------------------------------------------
+
+Submit a review to the ``openstack/requirements`` project removing the
+project from ``projects.txt``.  This needs to happen for stable
+branches as well.
+
+Steps 2-4: Remove Project from OpenDev and Retire it
+----------------------------------------------------
+
+Follow the steps about `Retiring a Project
+<https://docs.openstack.org/infra/manual/drivers.html#retiring-a-project>`_
+in the OpenDev Manual.
+
+
+Step 5: Remove Repository from the Governance Repository
+--------------------------------------------------------
+
+Remove the repository from the ``reference/projects.yaml`` file and
+add it to the file ``reference/legacy.yaml`` in the
+``openstack/governance`` repository. Note that if the project was
+recently active, this may have implications for automatic detection of
+ATCs.