diff --git a/lib/git.class.php b/lib/git.class.php
index 8828fa8..6833859 100644
--- a/lib/git.class.php
+++ b/lib/git.class.php
@@ -402,15 +402,37 @@ public function getObject($name)
 	return $object;
     }
 
+    /**
+     * @brief Look up a tag.
+     *
+     * @param $commit_obj (GitObject) The commit to look up.
+     * @returns (string) The commit of the tag.
+     */
+    public function getTag($commit_obj)
+    {
+        $commit = sha1_hex($commit_obj->getName());
+        $dir = $this->dir.'/refs/tags';
+        $d = opendir($dir);
+        while( ($file = readdir($d))!==false ) {
+            $fn = $dir."/".$file;
+            if( is_file($fn) ) {
+                if( $commit==trim(file_get_contents($fn)) ) {
+                    return $file;
+                }
+            }
+        }
+        return "";
+    }
+
     /**
      * @brief Look up a branch.
      *
      * @param $branch (string) The branch to look up, defaulting to @em master.
      * @returns (string) The tip of the branch (binary sha1).
      */
-    public function getTip($branch='master')
+    public function getTip($tip='master', $is_tag=false)
     {
-	$subpath = sprintf('refs/heads/%s', $branch);
+	$subpath = sprintf('refs/%s/%s', $is_tag?"tags":"heads", $tip);
 	$path = sprintf('%s/%s', $this->dir, $subpath);
 	if (file_exists($path))
 	    return sha1_bin(file_get_contents($path));
@@ -432,7 +454,7 @@ public function getTip($branch='master')
 	    if ($head !== NULL)
 		return $head;
 	}
-	throw new Exception(sprintf('no such branch: %s', $branch));
+	throw new Exception(sprintf('no such %s: %s', $is_tag?"tag":"branch", $tip));
     }
 }