add autoscroll to build trace

app/assets/javascripts/application.js

@@ -14,10 +14,15 @@
 //= require jquery_ujs
 //= require_tree .
 //
-function getBuild(buildPath, buildId) { 
+function getBuild(buildPath, buildId) {
   console.log('run');
   setTimeout(function() {
     $.get(buildPath + ".js?bid=" + buildId);
   }, 3000);
 }
+function checkAutoscroll() {
+  if('enabled' === $("#autoscroll-button").data('state')) {
+    $("html,body").scrollTop($("#build-trace").height());
+  }
+}

app/assets/javascripts/builds.js.coffee

+$(document).ready ->
+  $("#autoscroll-button").bind "click", ->
+    state = $(this).data("state")
+    if "enabled" is state
+      $(this).data "state", "disabled"
+      $(this).text "enable autoscroll"
+    else
+      $(this).data "state", "enabled"
+      $(this).text "disable autoscroll"

app/assets/stylesheets/main.scss

@@ -80,6 +80,10 @@ pre.trace {
   overflow-y: hidden;
 }
+.autoscroll-container {
+  margin-bottom: 5px;
+}
+
 .navbar .navbar-inner { border-radius: 0; }
 .builds {

app/views/builds/show.html.haml

@@ -61,9 +61,14 @@
             #{@build.git_commit_message}
     .clearfix
+    - if @build.active?
+      .autoscroll-container.pull-right
+        %button.btn.btn-mini#autoscroll-button{:type => "button", :data => {:state => 'disabled'}} enable autoscroll
+      .clearfix
     %pre.trace#build-trace
       = preserve do
         = raw @build.trace_html
+
   .span3
     .builds
       %h5 Builds for #{@build.short_sha}:

app/views/builds/show.js.haml

@@ -2,6 +2,7 @@
   :plain
     $('#build-trace').html("#{escape_javascript(@build.trace_html)}");
     $('#build-trace').append('#{loader_html}');
+    checkAutoscroll();
     getBuild('#{project_build_path(@project, @build)}', '#{@build.id}');
 - else
   :plain