milo: source and bot links

appengine/cmd/milo/frontend/templates/buildbot/pages/build.html

 {{define "title"}}{{.Build.Summary.Label}}{{end}}
 
 {{define "head"}}{{end}}
 
 {{define "body"}}
   <div class="content">
     <h1>{{.Build.Summary.Label}}</h1>
 
     <div class="column">
 
@@ skipping 40 matching lines @@
       {{ end }}
 
       {{ if .Commit.ChangelistURL }}
         <tr><td class="left">Patch</td><td><a href="{{.Commit.ChangelistURL}}">YES</a></td></tr>
       {{ end }}
 
       </table>
       {{ end }}  <!-- with -->
       {{ end }}  <!-- if -->
 
-      {{ if .Build.Summary.Bot }}
+      {{ if or .Build.Summary.Bot .Build.Summary.Source }}
       <h2>Execution:</h2>
-      <a href="{{ .Build.Summary.Bot.URL }}">{{ .Build.Summary.Bot.Label }}</a>
-      {{ end }}
+      <ul>
+        {{ if .Build.Summary.Source }}
+        <li>
+          Source:
+          <a href="{{ .Build.Summary.Source.URL }}">{{ .Build.Summary.Source.Label }}</a>
+        </li>
+        {{ end }}
+
+        {{ if .Build.Summary.Bot }}
+        <li>
+          Bot:
+          <a href="{{ .Build.Summary.Bot.URL }}">{{ .Build.Summary.Bot.Label }}</a>
+        </li>
+        {{ end }}
+      </ul>
+      {{ end }} <!-- if -->
 
       {{ if .Build.SourceStamp }}
         {{ if .Build.SourceStamp.Source }}
           <h2>Reason:</h2>
           <p>{{ .Source }}</p>
         {{ end }}
       {{ end }}
 
       <h2>Steps and Logfiles:</h2>
       <ol>
@@ skipping 99 matching lines @@
 <script>
 (function() {
   'use strict';
   var startedSpan = document.getElementById('started-time');
   var finishedSpan = document.getElementById('finished-time');
   startedSpan.textContent = milo.formatDate('{{ .Build.Summary.Started }}');
   finishedSpan.textContent = milo.formatDate('{{ .Build.Summary.Finished }}');
 })();
 </script>
 {{end}}