Update doc

docs/plugins.rst

@@ -101,6 +101,11 @@ Copyright plugin
 
 .. automodule:: sigal.plugins.copyright
 
+Encrypt plugin
+==============
+
+.. automodule:: sigal.plugins.encrypt
+
 Extended caching plugin
 =======================
 
@@ -136,7 +141,3 @@ ZIP Gallery plugin
 
 .. automodule:: sigal.plugins.zip_gallery
 
-Encrypt plugin
-==============
-
-.. automodule:: sigal.plugins.encrypt

sigal/plugins/encrypt/encrypt.py

@@ -49,6 +49,14 @@ the first build, so that incremental builds can share the same credentials.
 DO NOT CHANGE THE PASSWORD OR OTHER CRYPTOGRAPHIC PARAMETERS ONCE A GALLERY IS 
 BUILT, or there will be inconsistency in encrypted files and viewers will not be able
 to see some of the images any more.
+
+.. _compatibility-with-encrypt:
+
+Compatibility with other plugins:
+
+- ``zip_gallery``: if you enable both this plugin and the ``zip_gallery`` plugin, 
+  the generated zip archives will contain encrypted images, which is generally 
+  meaningless since viewers cannot easily decrypt them outside a browser.
 '''
 
 import os

sigal/plugins/zip_gallery.py

@@ -27,6 +27,8 @@ To ignore a ZIP gallery generation for a particular album, put
 a ``.nozip_gallery`` file next to it in its parent folder. Only the existence
 of this ``.nozip_gallery`` file is tested.  If no ``.nozip_gallery`` file is
 present, then make a ZIP archive with all media files.
+
+See :ref:`compatibility with the encrypt plugin <compatibility-with-encrypt>`.
 """
 
 import logging