The trick was using svn switch:
svn checkout
http://svn.wikimedia.org/svnroot/mediawiki/trunk/phase3
cd phase3
svn switch
http://svn.wikimedia.org/svnroot/mediawiki/trunk/extensions extensions/
--depth immediates
cd extensions/
svn checkout
http://svn.wikimedia.org/svnroot/mediawiki/trunk/extensions/SportsTeam
--depth infinity
cd ../..
svn up phase3
U phase3/extensions/SportsTeams/SportsTeams.i18n.php
U phase3/includes/parser/Parser.php
Updated to revision 100758.