Fix oopsie from me using version.py on an existing version

RELEASE-NOTES.md

@@ -56,9 +56,6 @@ END TEMPLATE-->
 
 ## 230.0.0
 
-
-## 223.0.0
-
 ### New features
 
 * Added `InterpolatedStringHandlerArgumentAttribute` to the sandbox whitelist.

Tools/version.py

@@ -45,6 +45,10 @@ def write_version(version: str, file_only: bool):
     # Verify
     verify_version(version)
 
+    if tag_exists(version):
+        print(f"Version tag already exists: v{version}")
+        sys.exit(1)
+
     update_release_notes(version)
 
     # Update
@@ -111,4 +115,8 @@ def undo_version(version: str):
     subprocess.run(["git", "reset", "--keep", "HEAD^"], check=True)
     print("Done (deleted commit saved as " + savename + ")")
 
+def tag_exists(version: str):
+    result = subprocess.run(["git", "tag", "-l", "v" + version], stdout=subprocess.PIPE, encoding="utf-8")
+    return bool(result.stdout.strip())
+
 main()