The MediaWiki-Installer supports the HTTP header Accept-Language. The HTTP header
Accept-Language: de-DE, de-AT;q=0.8, de-CH;q=0.6, de;q=0.4, nl;q=0.2
leads to the language code de-AT.
Expected language code is de-DE or de.
Steps to reproduce:
$ curl -L -H 'Accept-Language: de-DE, de-AT;q=0.8, de-CH;q=0.6, de;q=0.4, nl;q=0.2' 'http://localhost/mediawiki/mw-config/' 2> /dev/null | head -2 <!DOCTYPE html> <html dir="ltr" lang="de-AT">