Doc tweaks and changelog for #1641 (fix #1621)

Author: sampsyo

docs/changelog.rst

@@ -23,6 +23,10 @@ The new features:
 * :doc:`/plugins/plexupdate`: A new ``library_name`` option allows you to select
   which Plex library to update. :bug:`1572` :bug:`1595`
 * Add new `include` config option to allow including external config files.
+* :doc:`/plugins/zero`: The plugin can now use a "whitelist" policy as an
+  alternative to the (default) "blacklist" mode. Thanks to :user:`adkow`.
+  :bug:`1621` :bug:`1641`
+
 
 Fixes:
 

docs/plugins/zero.rst

@@ -5,6 +5,10 @@ The ``zero`` plugin allows you to null fields in files' metadata tags. Fields
 can be nulled unconditionally or conditioned on a pattern match. For example,
 the plugin can strip useless comments like "ripped by MyGreatRipper."
 
+The plugin can work in one of two modes. The first mode, the default, is a
+blacklist, where you choose the tags you want to remove. The second mode is a
+whitelist, where you instead specify the tags you want to keep.
+
 To use the ``zero`` plugin, enable the plugin in your configuration
 (see :ref:`using-plugins`).
 
@@ -20,7 +24,7 @@ fields to nullify and the conditions for nullifying them:
   embedded in the media file.
 * Set ``keep_fields`` to *invert* the logic of the plugin. Only these fields
   will be kept; other fields will be removed. Remember to set only
-  ``fields`` or ``keep_fields``, not both!
+  ``fields`` or ``keep_fields``---not both!
 * To conditionally filter a field, use ``field: [regexp, regexp]`` to specify
   regular expressions.
 * By default this plugin only affects files' tags ; the beets database is left
@@ -34,10 +38,6 @@ For example::
         genre: [rnb, 'power metal']
         update_database: true
 
-The plugin can work in one of two modes. The first mode, the default,
-is a blacklist, where you choose the tags you want to remove. The second mode
-is a whitelist where you instead specify the tags you want to keep.
-
 If a custom pattern is not defined for a given field, the field will be nulled
 unconditionally.