Introduce --fast

iIf we find and issue created for a commit that should have
been backported, it most probably means that we don't need to
keep looking for more backportable commits since we already processed
them when we processed the commit that created said issue

create-issues.py

 #!/usr/bin/env python3
 
+import argparse
 import json
 import os
 import requests
 import subprocess
 
+parser = argparse.ArgumentParser(description='Create gitlab issues from Pick-to: commits.')
+parser.add_argument('--fast', help='Skip looking for commits after we found a commit for which an issue has already been created', action="store_true")
+args = parser.parse_args()
+
 gitlab_token = os.environ.get('GITLAB_TOKEN')
 
 if not gitlab_token:
@@ -54,4 +59,6 @@ for qt5submodule in qt5submodules.splitlines():
                     quit()
                 
                 print("Created new issue: " + title)
+            elif args.fast:
+                break