Do not rebuild image if Dockerfile wasn't changed

Signed-off-by: Vitaliy Potyarkin <v.potyarkin@yadro.com>

.forgejo/workflows/build.yml

@@ -13,13 +13,29 @@ jobs:
         tag:
           - openjdk-11-maven-3.8.6
     steps:
-      - uses: actions/checkout@v3
-        with:
-          fetch-depth: 0
+      - name: Clone git repo
+        uses: actions/checkout@v3
 
-      - run: apt update; apt install -y buildah
-      - run: make ${{matrix.tag}}
-      - run: make ${{matrix.tag}} PUSH=y
-        if: github.ref == 'refs/heads/master' && github.event_name == 'push'
+      - name: List modified files
+        uses: tj-actions/changed-files@v45
+        with:
+          files: |
+            ${{matrix.tag}}/**
+        id: changed
+
+      - name: Install Buildah
+        run: apt update; apt install -y buildah
+        if: steps.changed.outputs.any_changed == 'true'
+
+      - name: Build OCI image
+        run: make ${{matrix.tag}}
+        if: steps.changed.outputs.any_changed == 'true'
+
+      - name: Push image to OCI registry
+        run: make ${{matrix.tag}} PUSH=y
+        if: >-
+          steps.changed.outputs.any_changed == 'true'
+          && github.ref == 'refs/heads/master'
+          && github.event_name == 'push'
         env:
           REGISTRY_PASSWORD: ${secrets.REGISTRY_PASSWORD}