[libgdata] docs: Expand privacy discussion in the libgdata documentation

[Philip Withnall <pwithnall src gnome org>]

commit 8240a4ddc9e8187987ae62361d854261b898037f
Author: Philip Withnall <philip withnall collabora co uk>
Date:   Tue Sep 20 17:05:28 2016 -0700

    docs: Expand privacy discussion in the libgdata documentation
    
    Mention HTTP versus HTTPS, and the need to encrypt files on disk if you
    are handling the user’s data (which you are with Google Drive).

 docs/reference/gdata-overview.xml |   11 +++++++++++
 1 files changed, 11 insertions(+), 0 deletions(-)
---
diff --git a/docs/reference/gdata-overview.xml b/docs/reference/gdata-overview.xml
index b795140..d2709d2 100644
--- a/docs/reference/gdata-overview.xml
+++ b/docs/reference/gdata-overview.xml
@@ -228,6 +228,17 @@
                                                Bugzilla</ulink>.</para>
                                </listitem>
                        </itemizedlist>
+
+                       <para>libgdata universally uses HTTPS rather than HTTP for communicating with 
servers. The port which is used may be changed
+                               for testing purposes, using the <envar>LIBGDATA_HTTPS_PORT</envar> 
environment variable; but the protocol used will
+                               always be HTTPS.</para>
+
+                       <para>libgdata provides ways to upload and download files, but does not implement 
code for loading or saving those files to
+                               or from disk. Since these files will typically be user data (such as their 
Google Drive documents), it is highly
+                               recommended that they are given restricted permissions, any temporary files 
are only readable by the current user,
+                               and files are potentially encrypted on disk where appropriate. The aim is to 
avoid leaking user data to other users
+                               of the system, or to attackers who gain access to the user’s hard drive 
(which may not be encrypted). libgdata itself
+                               only guarantees that data is encrypted while being sent over the 
network.</para>
                </refsect2>
        </refsect1>
 </refentry>