add tag prefix for docker images

docker/README.md

@@ -20,6 +20,7 @@ Build a Docker image and push it to the Gitea container registry
 | `ARTIFACT_NAME` | <p>Name of the build artifact to download</p> | `false` | `dist` |
 | `ARTIFACT_PATH` | <p>Destination path for the downloaded artifact</p> | `false` | `dist` |
 | `TAG_LATEST` | <p>Also tag and push the image as latest</p> | `false` | `false` |
+| `TAG_PREFIX` | <p>Optional prefix to prepend to IMAGE_TAG (e.g. 'dev' produces 'dev-&lt;tag&gt;'). Does not affect the latest tag.</p> | `false` | `""` |
 | `WORKING_DIRECTORY` | <p>Working directory for the Docker build</p> | `false` | `.` |
 <!-- action-docs-inputs source="action.yml" -->
 

docker/action.yml

@@ -28,6 +28,9 @@ inputs:
   TAG_LATEST:
     description: "Also tag and push the image as latest"
     default: "false"
+  TAG_PREFIX:
+    description: "Optional prefix to prepend to IMAGE_TAG (e.g. 'dev' produces 'dev-<tag>'). Does not affect the latest tag."
+    default: ""
   WORKING_DIRECTORY:
     description: "Working directory for the Docker build"
     default: "."
@@ -51,7 +54,11 @@ runs:
     - name: Docker Build and Push
       shell: sh
       run: |
-        TAGS="-t ${{ inputs.IMAGE_PATH }}:${{ inputs.IMAGE_TAG }}"
+        TAG="${{ inputs.IMAGE_TAG }}"
+        if [ -n "${{ inputs.TAG_PREFIX }}" ]; then
+          TAG="${{ inputs.TAG_PREFIX }}-${TAG}"
+        fi
+        TAGS="-t ${{ inputs.IMAGE_PATH }}:${TAG}"
         if [ "${{ inputs.TAG_LATEST }}" = "true" ]; then
           TAGS="$TAGS -t ${{ inputs.IMAGE_PATH }}:latest"
         fi