If $wgMessagesDirs is initially empty, we can optimize when batch loading
extensions:
if ( !$wgMessagesDirs ) {
$wgMessagesDirs = $cache['MessagesDirs'];
}
With APC, this should be O(1) CPU time.
This was suggested by Tim in the code review of I7074b65d07c5.
Change-Id: I66fa907cdaafe18b74b5b9afaa8b6b1db069bea3
Currently LocalisationCache merges the core data for all languages in
the fallback chain, then the extension data, then merges those two, and
then gives extensions like LocalisationUpdate a chance to make final
overrides with the LocalisationCacheRecache hook.
But if LocalisationUpdate doesn't want to locally duplicate all the
messages for every language (e.g. r104041), LocalisationCacheRecache is
too late: the information as to whether a message came from the primary
language or a fallback has been lost, so when LU itself has an override
for a fallback language it can't know whether or not the existing
message should be overridden or not.
The solution is for LocalisationCache to gather the data for each
fallback language separately, call a new hook for LU to affect just that
language (LocalisationCacheRecacheFallback), and only then merge the
fallback languages together.
Bug: 68781
Change-Id: Iacfe96063fcc66c1f97ca5e5292a8fc70af988cf
