Add alternative plugin update

13 April some new plugins were released leading old jenkins to be
inoperable. Adding semi-pin mechanism will allow us to handle it.

PROD-36857

Change-Id: Ic3d38cb9f86e16c316fb221e8a9d770dc1f5f400
diff --git a/README.rst b/README.rst
index 42bcbeb..96e6b1e 100644
--- a/README.rst
+++ b/README.rst
@@ -465,6 +465,29 @@
             enabled: false
           plugin5: absent
 
+Alternative plugin management using version pins (baseline plugin management could not work with some
+modern version labels like "1.12+build.201809061734").
+
+.. code-block:: yaml
+
+    jenkins:
+      client:
+        plugin:
+          alt_update:
+            enabled: True
+            base_url: https://archives.jenkins-ci.org/plugins/
+            jenkins_home_volume_dir: /srv/volumes/jenkins/
+            plugins:
+              ace-editor:
+                source_hash: abc97028893c8a71581a5f559ea48e8e1f1a65164faee96dabfed9e95e9abad2
+                version: '1.1'
+              ant:
+                source_hash: f04961a8a42f1e2ccdf5001d33ae93fdc2b3a5af96f13bddc1d721f1d11a8b4b
+                version: '1.8'
+              apache-httpcomponents-client-4-api:
+                enabled: False
+
+
 Adding plugin params to job:
 
 .. code-block:: yaml