Only allow steps of workflow to execute if running out of the mikebrady/shairport-sync GitHub repository

.github/workflows/docker.yml

@@ -2,6 +2,9 @@ name: Docker
 
 # Thanks to Ryan Govostes <https://github.com/rgov> for this workflow.
 
+# Using 'if:' conditions, the script will not execute the steps
+# unless it is running out of the 'mikebrady/shairport-sync' GitHub repository.
+
 on:
   push:
     # Publish `master` as Docker `latest` image.
@@ -28,6 +31,7 @@ jobs:
       # See: https://github.com/crazy-max/ghaction-docker-buildx/issues/134
       - name: Prepare
         id: prepare
+        if: github.repository == 'mikebrady/shairport-sync'
         run: |
           # Map git ref branch or tag name to Docker tag version
           VERSION=$(echo "${{ github.ref }}" | sed -e 's,.*/\(.*\),\1,')
@@ -48,17 +52,18 @@ jobs:
       - uses: crazy-max/ghaction-docker-buildx@v1.2.1
 
       - name: Build
+        if: github.repository == 'mikebrady/shairport-sync'
         run: |
           docker buildx build \
             --output type=image,push=false \
             ${{ steps.prepare.outputs.buildx_args }}
 
       - name: Log into registry
-        if: github.event_name == 'push'
+        if: github.event_name == 'push' && github.repository == 'mikebrady/shairport-sync'
         run: echo "${{ secrets.DOCKER_HUB_TOKEN }}" | docker login --username $DOCKER_HUB_USER --password-stdin
 
       - name: Push to registry
-        if: github.event_name == 'push'
+        if: github.event_name == 'push' && github.repository == 'mikebrady/shairport-sync'
         run: |
           docker buildx build \
             --output type=image,push=true \