Use last commit date instead of unix mtime

* simplify last website mtime script
* link appropriate commit to last mtime

html/includes/mtime.php

@@ -1,6 +1,5 @@
 <?php
-  date_default_timezone_set('Europe/Paris');
-  $mtime =  date("d M Y H:i:s", filemtime($this_file));
-  setlocale(LC_TIME, 'fr_FR.utf8','fra');
+  $last_rev = exec('git log -1 --pretty=format:"%H" '.$this_file);
+  $mtime = exec('LANG="fr_FR.UTF-8" git log -1 --pretty="format:%cr" '.$this_file);
 ?>
-<p style="text-align:right;">Mis à jour le <?php echo strftime("%d %B %Y à %H:%M:%S UTC%z", strtotime($mtime)); ?></p>
+<p style="text-align:right;">Dernière mise à jour <a href="https://git.gnous.fr/gnous/main_website/commit/<?php echo $last_rev;?>" target="_blank"><?php echo $mtime; ?></a></p>