CacheBuster is suboptimal

[halfdan]

The cache buster is generating a hash from several changing properties:

$pluginList = md5(implode(",", !$pluginNames ? Manager::getInstance()->getLoadedPluginsName() : $pluginNames));
$cacheBuster = md5(SettingsPiwik::getSalt() . $pluginList . PHP_VERSION . Version::VERSION . trim($currentGitHash));

Things to note:

• md5 is used twice
• SettingsPiwik::getSalt() is a static value.

[anonymous-matomo-user]

In 74e9976: Simplify cache buster and use only values that can change.

fixes #4567

[robocoder]

With git, I suppose devs commit more frequently. But just for historical context, I included the salt because I would frequently erase my config and re-install from my workspace without committing anything to svn.

[halfdan]

Makes sense - but changing the salt wouldn't have any effect on the assets/cache.