Fixed #21219 -- Added a way to set different permission for static files.

Previously, when collecting static files, the files would receive permission
from FILE_UPLOAD_PERMISSIONS. Now, there's an option to give different
permission from uploaded files permission by subclassing any of the static
files storage classes and setting the file_permissions_mode parameter.

Thanks dblack at atlassian.com for the suggestion.

docs/ref/contrib/staticfiles.txt

@@ -32,8 +32,6 @@ following settings:
 Management Commands
 ===================
 
-.. highlight:: console
-
 ``django.contrib.staticfiles`` exposes three management commands.
 
 collectstatic
@@ -61,6 +59,30 @@ receives all command line options of :djadmin:`collectstatic`. This is used
 by the :class:`~django.contrib.staticfiles.storage.CachedStaticFilesStorage`
 by default.
 
+By default, collected files receive permissions from
+:setting:`FILE_UPLOAD_PERMISSIONS`. If you would like different permissions for
+these files, you can subclass either of the :ref:`static files storage
+classes <staticfiles-storages>` and specify the ``file_permissions_mode``
+parameter. For example::
+
+    from django.contrib.staticfiles import storage
+
+    class MyStaticFilesStorage(storage.StaticFilesStorage):
+        def __init__(self, *args, **kwargs):
+            kwargs['file_permissions_mode'] = 0o640
+            super(CustomStaticFilesStorage, self).__init__(*args, **kwargs)
+
+Then set the :setting:`STATICFILES_STORAGE` setting to
+``'path.to.MyStaticFilesStorage'``.
+
+.. versionadded:: 1.7
+
+    The ability to override ``file_permissions_mode`` is new in Django 1.7.
+    Previously the file permissions always used
+    :setting:`FILE_UPLOAD_PERMISSIONS`.
+
+.. highlight:: console
+
 Some commonly used options are:
 
 .. django-admin-option:: --noinput
@@ -174,6 +196,8 @@ Example usage::
 
     django-admin.py runserver --insecure
 
+.. _staticfiles-storages:
+
 Storages
 ========