add --file option to cookbook site download

includes_knife/includes_knife_site_cookbook_download_options.rst

@@ -8,5 +8,8 @@ This argument has the following options:
 ``COOKBOOK_VERSION``
    |COOKBOOK_VERSION download|
 
-``-f``, ``--force``
+``-f FILE``, ``--file FILE``
+   |file cookbook_download|
+
+``--force``
    |force directory|

swaps/swap_descriptions.txt

@@ -401,6 +401,7 @@
 .. |file atomic_update| replace:: Use to apply atomic file updates to all resources. Set to ``true`` for global atomic file updates. Set to ``false`` for global non-atomic file updates. (Use the ``atomic_update`` setting on a per-resource basis to override this setting.)
 .. |file azure_publish_settings| replace:: The name of the |windows azure_publish_settings| file, including the path. For example: ``"/path/to/your.publishsettings"``.
 .. |file cache_path| replace:: The location in which cookbooks (and other transient data) files are stored when they are synchronized. (This value can also be used in recipes to download files with the ``remote_file`` resource.)
+.. |file cookbook_download| replace:: The file to which a cookbook download is written.
 .. |file local_settings| replace:: The name of the local settings file to be generated by a template.
 .. |file private_key| replace:: Use to save a private key to the specified file name.
 .. |file public_key| replace:: All users are assigned a public key. Use to write the public key to a file.