ci: skip build and publish when upstream versions are unchanged

.gitea/workflows/image.yaml

@@ -19,16 +19,21 @@ jobs:
         with:
           persist-credentials: false
       - name: Check upstream versions
+        id: update
         if: github.event_name != 'push'
-        run: python3 scripts/update.py
+        run: |
+          set -eu
+          python3 scripts/update.py
+          if git diff --quiet -- versions.env; then echo changed=false; else echo changed=true; fi >> "$GITHUB_OUTPUT"
       - name: Build and test
+        if: github.event_name == 'push' || steps.update.outputs.changed == 'true'
         run: |
           set -eu
           . ./versions.env
           docker build --pull --build-arg COREDNS_VERSION="$COREDNS_VERSION" --build-arg MYSQL_PLUGIN_REV="$MYSQL_PLUGIN_REV" -f dockerfile -t coredns-mysql:ci .
           scripts/test-image.sh coredns-mysql:ci "$COREDNS_VERSION"
       - name: Commit and push updated versions
-        if: github.event_name != 'push'
+        if: github.event_name != 'push' && steps.update.outputs.changed == 'true'
         env:
           GIT_HOST: ${{ vars.GIT_HOST }}
           GIT_NAME: ${{ vars.GIT_NAME }}
@@ -37,7 +42,6 @@ jobs:
           GIT_TOKEN: ${{ secrets.GIT_TOKEN }}
         run: |
           set -eu
-          if git diff --quiet -- versions.env; then exit 0; fi
           test -n "$GIT_HOST" && test -n "$GIT_NAME" && test -n "$GIT_EMAIL" && test -n "$REGISTRY_USER" && test -n "$GIT_TOKEN"
           git config user.name "$GIT_NAME"
           git config user.email "$GIT_EMAIL"
@@ -49,6 +53,7 @@ jobs:
           chmod 700 "$askpass"
           GIT_ASKPASS="$askpass" GIT_TERMINAL_PROMPT=0 git push "https://${GIT_HOST}/${GITHUB_REPOSITORY}.git" HEAD:refs/heads/main
       - name: Publish image
+        if: github.event_name == 'push' || steps.update.outputs.changed == 'true'
         env:
           GIT_HOST: ${{ vars.GIT_HOST }}
           REGISTRY_USER: ${{ vars.REGISTRY_USER }}