New message as requested.\n Only displayed on full help and when no arguments is passed

tools/sigma/sigmac.py

@@ -1,7 +1,6 @@
 #!/usr/bin/env python3
 # A Sigma to SIEM converter
 # Copyright 2016-2017 Thomas Patzke, Florian Roth
-import os
 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU Lesser General Public License as published by
 # the Free Software Foundation, either version 3 of the License, or
@@ -65,6 +64,12 @@ ERR_FULL_FIELD_MATCH    = 90
 # Allowed fields in output
 allowed_fields = ["title", "id", "status", "description", "author", "references", "fields", "falsepositives", "level", "tags", "filename"]
 
+deprecation_warning_message = colored("Sigmac will be deprecated by the end of 2022",
+                                      "red") + " in favour of sigma-cli and pySigma. Please " +  colored("stop contributing backends", "red") + \
+                                               " to this tool. Limited support is offered until the end of 2023, " \
+                                               "especially for backends that haven't been migrated yet.\n "
+
+
 def alliter(path):
     for sub in path.iterdir():
         if sub.name.startswith("."):
@@ -97,7 +102,7 @@ class ActionBackendHelp(argparse.Action):
 def set_argparser():
     """Sets up and parses the command line arguments for Sigmac.
     Returns the argparser"""
-    argparser = argparse.ArgumentParser(description="Convert Sigma rules into SIEM signatures.")
+    argparser = argparse.ArgumentParser(description="Convert Sigma rules into SIEM signatures.\n" + deprecation_warning_message, formatter_class=argparse.RawTextHelpFormatter)
     argparser.add_argument("--recurse", "-r", action="store_true", help="Use directory as input (recurse into subdirectories is not implemented yet)")
     argparser.add_argument("--filter", "-f", help="""
     Define comma-separated filters that must match (AND-linked) to rule to be processed.
@@ -183,9 +188,6 @@ def main():
     cmdargs = argparser.parse_args()
     scm = SigmaConfigurationManager()
 
-    print(colored("!!! WARNING", "red"), "sigmac is deprecated in favor of", colored("sigma-cli", "green"), "using", colored("pySigma", "green"), ". Please stop contributing backends to this tool, it will be removed in 2023.")
-    print()
-
     logger = logging.getLogger(__name__)
     if cmdargs.debug:   # pragma: no cover
         logging.basicConfig(filename='sigmac.log', filemode='w', level=logging.DEBUG)
@@ -205,6 +207,7 @@ def main():
         sys.exit(0)
     elif len(cmdargs.inputs) == 0:
         print("Nothing to do!")
+        print(deprecation_warning_message)
         argparser.print_usage()
         sys.exit(0)