hgweb: add reset javascript function to Graph

It makes the Graph object to be in the same state as just after
the initialization. This will help to add infinite scrolling to graph view.

mercurial/templates/static/mercurial.js

@@ -36,6 +36,14 function Graph() {
 	this.columns = 0;
 	this.revlink = '';
 
+	this.reset = function() {
+		this.bg = [0, 4];
+		this.cell = [2, 0];
+		this.columns = 0;
+		document.getElementById('nodebgs').innerHTML = '';
+		document.getElementById('graphnodes').innerHTML = '';
+	}
+
 	this.scale = function(height) {
 		this.bg_height = height;
 		this.box_size = Math.floor(this.bg_height / 1.2);