My proposal to implement @brianteeman suggestion of refresh assets after version updates.

This method creates two new methods to JDocument to allow to load versionable assets:

public function addScriptVersion($url, $version = null, $type = "text/javascript", $defer = false, $async = false)

and:

public function addStyleSheetVersion($url, $version = null, $type = "text/css", $media = null, $attribs = array())

The CMS is able to handle assets versions automatically but third part developers can also specify the assets versions.

Example to allow the system to automatically add version:

$doc->addScriptVersion('templates/' . $this->template . '/js/template.js');

Example to specify the asset version manually:

$doc->addScriptVersion('templates/' . $this->template . '/js/template.js', '1,87');

The automatic version is generated only:

• When the user session is created
• On each page load when debug is enabled.

So in the normal mode it would be created only 1 time per user session instead of 1 per page load. The version is built with:

$mediaTag = md5($this->getLongVersion() . $config->get('secret') . $date->toSql());

It uses Joomla! version + secret string in configuration + current date + time.

It also includes one extra check to not add mediatag to assets that already contain it. So in most cases in can directly replace addScript & addStylesheet methods.

This modifies JFactory to add the mediatag on document creation. I saw that JFactory is already using JVersion so it doesn't add additional dependencies. But with this same method we can do it outside JFactory (for example inside a template) with:

$doc->setMediatag('23424235346456');

Anyone can flush assets cache with:

$app = JFactory::getApplication()->flushAssets();

This pull request already includes the code to refresh assets in:

1. In finaliseUpgrade() method triggered after upgrading joomla.
2. In the extension installer after install(), discover_install() & uninstall() methods.

Feature tracker issue:
http://joomlacode.org/gf/project/joomla/tracker/?action=TrackerItemEdit&tracker_item_id=31602

Google group discussion (please send your comments there to avoid duplicated discussions):
https://groups.google.com/forum/#!topic/joomla-dev-cms/81ZQ94MCV9A