The Potlatch 2 styles need to be patched in order to work with the JOSM MapCSS implementation.

Potlatch 2's repository is git://git.openstreetmap.org/potlatch2.git

 * 'source' contains the unmodified source files copied from git.openstreetmap.org/potlatch2.git/history/master:/resources/stylesheets.
 * 'patched' contains the manually edited version.
 * The ant task 'assemble' concatinates the patched files to the final style 'styles/standard/potlatch2.mapcss'

When updating from upstream, keep all 3 in sync.

At time of writing, the last update used 0f12f406e80e7cedb1ca9d4662ab2977077fdc79 but better check the commit dates as well.