The Potlatch 2 styles need to be patched in order to work with the JOSM MapCSS implementation. The subversion externals definition has an explicit revision number set. When updating from the remote repository, make sure to change the patched files accordingly. The ant task 'assemble' concatinates the patched files to the final style potlatch2.mapcss Another ant task 'update-externals' is a shortcut to change the svn property, such that the externals points to the revision that is currently checked out. When committing, the following should be in sync: * revision number in the svn externals property * patched *.css files * styles/standard/potlatch2.mapcss