Write thumbnails doc & add changelog entry

docs/changelog.rst

@@ -28,6 +28,8 @@ Features:
   ``art_filename`` configuration option. :bug:`1258`
 * :doc:`/plugins/fetchart`: There's a new Wikipedia image source that uses
   DBpedia to find albums. Thanks to Tom Jaspers. :bug:`1194`
+* A new :doc:`/plugins/thumbnails` generates thumbnails with cover art for
+  album folders for all freedesktop.org-compliant file managers.
 
 Core changes:
 

docs/plugins/index.rst

@@ -70,6 +70,7 @@ Each plugin has its own set of options that can be defined in a section bearing
    smartplaylist
    spotify
    the
+   thumbnails
    types
    web
    zero
@@ -156,6 +157,7 @@ Miscellaneous
   on regular expressions.
 * :doc:`spotify`: Create Spotify playlists from the Beets library.
 * :doc:`types`: Declare types for flexible attributes.
+* :doc:`thumbnails`: Get thumbnails with the cover art on your album folders.
 * :doc:`web`: An experimental Web-based GUI for beets.
 
 .. _MPD: http://www.musicpd.org/

docs/plugins/thumbnails.rst

@@ -0,0 +1,35 @@
+Thumbnails Plugin
+==================
+
+The ``thumbnails`` plugin creates thumbnails your for album folders with the
+album cover. This works on freedesktop.org-compliant file managers such as
+Nautilus or Thunar, and is therefore POSIX-only.
+
+To use the ``thumbnails`` plugin, enable it (see :doc:`/plugins/index`) as well
+as the :doc:`/plugins/fetchart`. As with :doc:`/plugins/embedart`, be sure to
+put ``fetchart`` before ``thumbnails`` in the ``plugins`` section of your
+config. You'll need 2 additional python packages: `pyxdg` and `pathlib`.
+
+``thumbnails`` needs to resize the covers, and therefore requires either
+`ImageMagick`_ or `PIL`_.
+
+.. _PIL: http://www.pythonware.com/products/pil/
+.. _ImageMagick: http://www.imagemagick.org/
+
+Configuration
+-------------
+
+To configure the plugin, make a ``thumbnails`` section in your configuration
+file. The available options are
+
+- **auto**: Whether the thumbnail should be automatically set on import.
+  Default: ``yes``.
+- **force**: Generate the thumbnail even when there's one that seems fine (more
+  recent than the cover art).
+  Default: ``no``.
+
+Usage
+-----
+
+The ``thumbnails`` command provided by this plugin creates a thumbnail for
+albums that match a query (see :doc:`/reference/query`).