The -package and -exclude options are difficult to use from within
Make or Ant because they require the option to be repeated
for each package/class.

For example, supposing an Ant property that contains a list
of packages, "java.lang,java.io". There is no mechanism
to split that into a variable number of arguments to be
passed to the Java command needed to run the Setup proceedure.

If the option accepted a list with any delimiter (",", ":", etc).
it would be a lot easier to automate generation of sig files.