Compares to JARs and filters out modified classes

get_changed.py

from zipfile import ZipFile
import sys

if len(sys.argv) < 4:
    print("python " + sys.argv[0] + " <unchanged.jar> <changed.jar> <output.jar>")
else:
    with ZipFile(sys.argv[1]) as unchanged:
        with ZipFile(sys.argv[2]) as changed:
            with ZipFile(sys.argv[3], "w") as output:
                for name in changed.namelist():
                    content = changed.read(name)
                    if name not in unchanged.namelist():
                        output.writestr(name, content)
                    elif content != unchanged.read(name):
                        output.writestr(name, content)