info: Add documentation for recent features

docs/changelog.rst

@@ -9,8 +9,9 @@ This release adds **sorting** to beets queries. See :ref:`query-sort`.
 Features:
 
 * :doc:`/plugins/info`: Files can be specified through library queries
-  and the `--library` option prints library fields instead of tags.
-  Tags and library fields can be summarized with `--summarize` option.
+  and the ``--library`` option prints library fields instead of tags.
+  Tags and library fields for multiple files can be summarized with the
+  ``--summarize`` option.
 
 Fixes:
 

docs/plugins/info.rst

@@ -12,5 +12,18 @@ Enable the plugin and then type::
 and the plugin will enumerate all the tags in the specified file. It also
 accepts multiple filenames in a single command-line.
 
+You can also enter a :doc:`query </reference/query>` to inspect music from
+your library::
+
+    $ beet info beatles
+
+Command-line options include:
+
+* ``--library`` or ``-l``: Show data from the library database instead of the
+  files' tags.
+* ``--summarize`` or ``-s``: Merge all the information from multiple files
+  into a single list of values. If the tags differ across the files, print
+  ``[various]``.
+
 .. _id3v2: http://id3v2.sourceforge.net
 .. _mp3info: http://www.ibiblio.org/mp3info/