Merge pull request #2412 from ReactionMechanismGenerator/minor_ci_update

CI: don't make destination directory for reference results when generating reference results

Author: hwpang

.github/workflows/CI.yml

@@ -149,6 +149,7 @@ jobs:
             test/regression
 
       - name: mkdir stable_regression_results
+        if: github.ref != 'refs/heads/main'
         run: mkdir stable_regression_results
 
       # Retrieve Stable Results for reference