add ability to set default tags in config

lib/ansible/cli/__init__.py

@@ -453,9 +453,9 @@ class CLI(with_metaclass(ABCMeta, object)):
                               help='the new vault identity to use for rekey')
 
         if subset_opts:
-            parser.add_option('-t', '--tags', dest='tags', default=[], action='append',
+            parser.add_option('-t', '--tags', dest='tags', default=C.TAGS_RUN, action='append',
                               help="only run plays and tasks tagged with these values")
-            parser.add_option('--skip-tags', dest='skip_tags', default=[], action='append',
+            parser.add_option('--skip-tags', dest='skip_tags', default=C.TAGS_SKIP, action='append',
                               help="only run plays and tasks whose tags do not match these values")
 
         if output_opts:

lib/ansible/config/base.yml

@@ -1436,6 +1436,22 @@ SYSTEM_WARNINGS:
   ini:
   - {key: system_warnings, section: defaults}
   type: boolean
+TAGS_RUN:
+  name: Run Tags
+  default: []
+  type: list
+  description: default list of tags to run in your plays, Skip Tags has precedence.
+  env: [{name: ANSIBLE_RUN_TAGS}]
+  ini:
+  - {key: run, section: tags}
+TAGS_SKIP:
+  name: Skip Tags
+  default: []
+  type: list
+  description: default list of tags to skip in your plays, has precedence over Run Tags
+  env: [{name: ANSIBLE_SKIP_TAGS}]
+  ini:
+  - {key: skip, section: tags}
 USE_PERSISTENT_CONNECTIONS:
   name: Persistence
   default: False