redmine/app/views/watchers/_set_watcher.js.erb

<% selector = ".#{watcher_css(watched)}" %>
$("<%= selector %>").each(function(){$(this).replaceWith("<%= escape_javascript watcher_link(watched, user) %>")});
$('#watchers').html('<%= escape_javascript(render(:partial => 'watchers/watchers', :locals => {:watched => watched.first})) %>');