Add suport for generating other sections in defaulter

defaulter

@@ -104,7 +104,7 @@ def process_file(fn: str, out_mapping: dict[str, list[str]]) -> None:
 			files = list(filter(lambda x: x != '', files.split(';')))
 			process_assignment(pat, files, out_mapping)
 
-def dump_mapping(mapping: dict[str, list[str]], filename: str = None) -> None:
+def dump_mapping(mapping: dict[str, list[str]], filename: str = None, header: str = '[Default Applications]') -> None:
 	if filename is None:
 		filename = '/dev/stdout'
 		path = Path(filename)
@@ -115,19 +115,35 @@ def dump_mapping(mapping: dict[str, list[str]], filename: str = None) -> None:
 	with open(path, 'w') as f:
 		def fprint(*a, **kwa): print(*a, **kwa | {'file': f})
 
-		fprint('[Default Applications]')
+		fprint(header)
 		for mimetype, desktop_files in mapping.items():
 			fprint(f"{mimetype}={';'.join(desktop_files)};")
 
+
+
 def main():
-	if '--help' in sys.argv or len(sys.argv) <= 1:
+	import argparse
-		print(f'Usage: {sys.argv[0]} file ...\n\nThis script processes regex-based rules for default applications.', file=sys.stderr)
+	parser = argparse.ArgumentParser()
-		sys.exit()
+	parser.description = 'This script processes regex-based rules for default applications.'
+	parser.add_argument('--add',  help="Generate [Added Associations] section instead", action='store_true')
+	parser.add_argument('--remove', help="Generate [Removed Associations] section instead", action='store_true')
+	parser.add_argument('files', help="Source of the rules", nargs='+')
+	parser.usage='%(prog)s [--add|--remove] files ...'
+	parser.epilog = 'By default a [Default Applications] section is created. There is no option to apply this behaviour.'
+
+	args = parser.parse_args()
+	if sum([args.add, args.remove]) > 1:
+		print('Cannot generate conflicting sections!', file=sys.stderr)
+		sys.exit(1)
+
+	params = {}
+	if args.add: params['header'] = '[Added Associations]'
+	if args.remove: params['header'] = '[Removed Associations]'
 
 	out_mapping = {}
-	for fn in sys.argv[1:]:
+	for fn in args.files:
 		process_file(fn, out_mapping)
-	dump_mapping(out_mapping)
+	dump_mapping(out_mapping, **params)
 
 
 # TODO: def resolve_more_specific_mimetypes(mimetype: str) -> list[str]: ...