Add registry login, default cache-from, and cache-from/to defaults

.gitea/actions/docker-build/action.yml

@@ -17,10 +17,19 @@ inputs:
     default: ""
   cache-from:
     description: Cache source (e.g. type=gha, or image:tag)
-    default: ""
+    default: type=local,src=/tmp/buildx-cache
   cache-to:
     description: Cache destination for buildx (type=gha or type=local)
     default: type=local,dest=/tmp/buildx-cache,mode=max
+  registry:
+    description: Docker registry for login (e.g. ghcr.io)
+    default: ""
+  registry-username:
+    description: Docker registry username
+    default: ""
+  registry-password:
+    description: Docker registry password (use secrets.DOCKER_PASSWORD)
+    default: ""
   platforms:
     description: Target platforms as CSV (e.g. linux/amd64,linux/arm64)
     default: linux/amd64
@@ -102,6 +111,12 @@ runs:
         echo "tag=$TAG" >> $GITHUB_OUTPUT
         echo "tags=$TAGS" >> $GITHUB_OUTPUT
 
+    - name: Log in to Docker registry
+      shell: bash
+      if: inputs.push == 'true' && inputs.registry != ''
+      run: |
+        echo "${{ inputs.registry-password }}" | docker login ${{ inputs.registry }} -u ${{ inputs.registry-username }} --password-stdin
+
     - name: Build image
       id: build
       shell: bash