hgweb: format page_nav of gitweb/error.tmpl and add missing links

mercurial/templates/gitweb/error.tmpl

@@ -12,7 +12,14 b''
 </div>
 
 <div class="page_nav">
-<a href="{url}summary{sessionvars%urlparameter}">summary</a> | <a href="{url}shortlog{sessionvars%urlparameter}">shortlog</a> | <a href="{url}log{sessionvars%urlparameter}">changelog</a> | <a href="{url}tags{sessionvars%urlparameter}">tags</a> | <a href="{url}file/{node|short}{sessionvars%urlparameter}">files</a><br/>
+<a href="{url}summary{sessionvars%urlparameter}">summary</a> |
+<a href="{url}shortlog{sessionvars%urlparameter}">shortlog</a> |
+<a href="{url}log{sessionvars%urlparameter}">changelog</a> |
+<a href="{url}tags{sessionvars%urlparameter}">tags</a> |
+<a href="{url}branches{sessionvars%urlparameter}">branches</a> |
+<a href="{url}file/{node|short}{sessionvars%urlparameter}">files</a> |
+<a href="{url}help{sessionvars%urlparameter}">help</a>
+<br/>
 </div>
 
 <div class="page_body">