man: add a note about $XDG_SEAT and $XDG_VTNR to pam_systemd(8)

Issue #6499 requests that a mention that those varibles can be set in the
environment is added. But the man page already says that. There isn't much
detail, but a man page does not need to and in this case should not include
all the details. Instead a note is added that those vars can be derived from
$DISPLAY.

Closes #6499.

diff --git a/man/pam_systemd.xml b/man/pam_systemd.xml
index f45631688c9f216a4286d7bb3fc6a26a526615be..a769a49bbebbaa5ded916b240a3a60f0996025ee 100644 (file)
--- a/man/pam_systemd.xml
+++ b/man/pam_systemd.xml
@@ -255,8 +255,11 @@
         for, if any. (Only applies to seats with a VT available, such
         as <literal>seat0</literal>)</para></listitem>
       </varlistentry>
-
     </variablelist>
+
+    <para>If not set, <command>pam_systemd</command> will determine the
+    values for <varname>$XDG_SEAT</varname> and <varname>$XDG_VTNR</varname>
+    based on the <varname>$DISPLAY</varname> variable.</para>
   </refsect1>
 
   <refsect1>