interpret empty string as None

Author: keewis

action.yaml

@@ -36,9 +36,4 @@ runs:
         ENVIRONMENT_PATHS: ${{ inputs.environment-paths }}
         TODAY: ${{ inputs.today }}
       run: |
-        if [[ "$TODAY" != "" ]]; then
-            opts=(--today="$TODAY")
-        else
-            opts=()
-        fi
-        python minimum_versions.py "$opts" --policy="$POLICY_PATH" $ENVIRONMENT_PATHS
+        python minimum_versions.py --today="$TODAY" --policy="$POLICY_PATH" $ENVIRONMENT_PATHS

minimum_versions.py

@@ -315,6 +315,9 @@ def format_bump_table(specs, policy_versions, releases, warnings, ignored_violat
 
 
 def parse_date(string):
+    if not string:
+        return None
+
     return datetime.datetime.strptime(string, "%Y-%m-%d").date()