* doc/apt.ent:

  - Add a note about APT_CONFIG in the -c description (Closes: #578267)

debian/changelog

@@ -27,6 +27,8 @@ apt (0.7.26~exp4) experimental; urgency=low
   * cmdline/apt-cache.cc:
     - align Installed and Candidate Version in policy so they can be compared
       easier, thanks Ralf Gesellensetter for the pointer! (Closes: #578657)
+  * doc/apt.ent:
+    - Add a note about APT_CONFIG in the -c description (Closes: #578267)
 
   [ Jari Aalto ]
   * cmdline/apt-get.cc:

doc/apt.ent

@@ -261,7 +261,9 @@
       <term><option>--config-file</option></term>
      <listitem><para>Configuration File; Specify a configuration file to use. 
      The program will read the default configuration file and then this 
-     configuration file. See &apt-conf; for syntax information.     
+     configuration file. If configuration settings need to be set before the
+     default configuration files are parsed specify a file with the <envar>APT_CONFIG</envar>
+     environment variable. See &apt-conf; for syntax information.
      </para>
      </listitem>
      </varlistentry>