sync missing versions to dockerhub regularly

.github/workflows/sync_missing_versions.yml

@@ -0,0 +1,19 @@
+on:
+  workflow_dispatch:
+  schedule:
+  - cron: '0 0 1 * *' # at 00:00 on 1st day of month
+jobs:
+  sync_missing_versions:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+
+      - name: Login to DockerHub
+        uses: docker/login-action@v1 
+        with:
+          username: ${{ secrets.DOCKERHUB_USERNAME }}
+          password: ${{ secrets.DOCKERHUB_TOKEN }}
+
+      - name: Sync missing versions
+        run: make sync_missing_versions
+

Makefile

@@ -47,7 +47,8 @@ sync_missing_versions:
 		NEXT_PAGE=$$(cat $$TMP/page.json | jq -rM '.next'); \
 	done; \
 	\
-	grep -v -x -f "$$TMP/promtool.tags" "$$TMP/prometheus.tags" > "$$TMP/missing.tags"; \
-	grep -v -x -f blacklist.tags "$$TMP/missing.tags" > "$$TMP/filtered_missing.tags"; \
+	(grep -v -x -f "$$TMP/promtool.tags" "$$TMP/prometheus.tags" > "$$TMP/missing.tags") || true; \
+	(grep -v -x -f blacklist.tags "$$TMP/missing.tags" > "$$TMP/filtered_missing.tags") || true; \
+	touch "$$TMP/filtered_missing.tags"; \
 	cat "$$TMP/filtered_missing.tags" | sort | xargs -I{} -n1 bash -c "make sync PROMTOOL_VERSION={}"; \
-	
+