The current javascript function @updateIssueFrom(url)@ does not return anything.
If we could just return the XMLHttpRequest object (as it is returned by the @ajax()@ call), it would allow us to chain methods like this:

updateIssueFrom(url).done(function() {
  $( this ).addClass( "done" );
});

Here is the patch:

diff --git a/public/javascripts/application.js b/public/javascripts/application.js
--- a/public/javascripts/application.js
+++ b/public/javascripts/application.js
@@ -471,7 +471,7 @@ function updateIssueFrom(url) {
   $('#all_attributes input, #all_attributes textarea, #all_attributes select').each(function(){
     $(this).data('valuebeforeupdate', $(this).val());
   });
-  $.ajax({
+  return $.ajax({
     url: url,
     type: 'post',
     data: $('#issue-form').serialize()

This simple patch could really help me to simplify my Redmine plugins. Thank you.