--attach=yes option will fail to start the client if the
--compress=0 option is used.
xpra start --attach=yes --start=xterm --daemon=no -z0 will produce:
xpra initialization error: no such option: --compression_level
Preface: unless your setup is very unusual (ie: a very low power CPU, or your installation is missing the lz4 compressor), then setting compression to zero will do absolutely nothing.
r20051 also includes a fix for an unintended variable name shadowing bug
this ticket has been moved to: https://github.com/Xpra-org/xpra/issues/1930