Prefer linking to REv2 Directory messages instead of Trees

This reduces the amount of load clicking through large output
directory hierarchies, as it no longer requires REv2 Tree objects to get
loaded constantly.

Author: EdSchouten

cmd/bb_browser/templates/page_action.html

@@ -128,8 +128,14 @@ <h2 class="my-4">Output files</h2>
 	{{range .OutputDirectories}}
 		<tr class="font-monospace">
 			<td style="white-space: nowrap">drwxr-xr-x</td>
-			<td style="text-align: right">{{.TreeDigest.SizeBytes}}</td>
-			<td style="width: 100%; word-break: break-all"><a class="text-success" href="../../tree/{{.TreeDigest.Hash}}-{{.TreeDigest.SizeBytes}}/">{{.Path}}</a>/</td>
+			{{$path := .Path}}
+			{{with .RootDirectoryDigest}}
+				<td style="text-align: right">{{.SizeBytes}}</td>
+				<td style="width: 100%; word-break: break-all"><a class="text-success" href="../../directory/{{.Hash}}-{{.SizeBytes}}/">{{$path}}</a>/</td>
+			{{else}}
+				<td style="text-align: right">{{.TreeDigest.SizeBytes}}</td>
+				<td style="width: 100%; word-break: break-all"><a class="text-success" href="../../tree/{{.TreeDigest.Hash}}-{{.TreeDigest.SizeBytes}}/">{{$path}}</a>/</td>
+			{{end}}
 		</tr>
 	{{end}}
 	{{range .OutputSymlinks}}