[VOL-5004] - Clone unit tests to run on a v2.12 branch

[VOL-5007]
[VOL-5010]

howto/release/preparation.rst
howto/release/ci-management/index.rst
howto/release/ci-management/create_lts_view.rst
-----------------------------------------------
  o Document new makefile targets added to help branch jenkins
  o jobs for release.

Change-Id: I79b27cb16a11c76417d5f6fc2458e4c2d1bee2e0
diff --git a/howto/release/ci-management/clone_and_branch_testing.rst b/howto/release/ci-management/clone_and_branch_testing.rst
new file mode 100644
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+Jenkins jobs: Release branching for unit tests
+==============================================
+
+Intent
+------
+
+With each new VOLTHA LTS release (v2.12, v2.11, v2.8) jenkins unit testing and
+sandbox tooling must be branched for release to protect testing from
+future enhancements on master branch.
+
+JJB configs used to generate pipeline jobs are maintained in a central
+repository, test suites are not maintained on distinct branches within
+revision control.  Instead versioning is implemented using naming conventions
+within the job configs.
+
+WIP:
+----
+
+Makefile target create-jobs-release will create a versioned hierarchy
+for VOLTHA test jobs.  Refactoring is still needed to modularize job
+definitions from the monolithic yaml job config that contains all
+jobs and versions.
+
+.. code-block:: shell-session
+   :caption: Clone and branch VOLTHA testing for release.
+   :linenos:
+   :emphasize-lines: 5,8,14
+
+   # Clone repo:ci-management
+   % git clone ssh://gerrit.opencord.org:29418/ci-management.git
+   % cd ci-management
+
+   % make help | grep release
+     help-voltha-release Display voltha release targets
+
+   % make help-voltha-release
+   [RELEASE] - Create branch driven testing pipelines
+     create-jobs-release
+     create-jobs-release-nightly Nightly testing
+     create-jobs-release-units   Unit testing
+
+   % make create-jobs-release voltha-version=voltha-2.12
+
+.. code-block:: shell-session
+   :caption: Jenkins (JJB) branched job configs created
+
+   % cd ci-management
+   % find jjb -name '*2.12*'
+
+   jjb/voltha-test/voltha-certification/voltha-2.12.yaml
+   jjb/voltha-test/voltha-nightly-jobs/voltha-2.12.yaml
+
+TODO
+----
+
+- Document the current testing setup and branching within monolithic yaml file.