Fix PR_COMMIT_RANGE on CI for PRs from forks (#2244)

.github/workflows/ci.yml

@@ -78,7 +78,7 @@ jobs:
             --target garage-dev \
             -t "${DOCKER_TAG}" \
             --build-arg GARAGE_GH_TOKEN \
-            --cache-from="docker.pkg.github.com/${OWNER}/${DOCKER_CACHE_REPO}/${DOCKER_TAG}"
+            --cache-from="rlworkgroup/garage"
       - name: Push to cache (GitHub Package Registry)
         run: |
           docker tag "${DOCKER_TAG}" "docker.pkg.github.com/${OWNER}/${DOCKER_CACHE_REPO}/${DOCKER_TAG}"
@@ -100,16 +100,20 @@ jobs:
 
     steps:
     - name: Login to GitHub Package Registry
-      if: github.event_name == 'pull_request' || github.event_name == 'repository_dispatch'
+      if: github.event_name == 'pull_request' || env.IS_PR_FROM_FORK
       run: echo ${{ secrets.CI_REGISTRY_TOKEN }} | docker login docker.pkg.github.com -u ${CI_USER} --password-stdin
     - name: Pull from cache (GitHub Package Registry)
-      if: github.event_name == 'pull_request' || github.event_name == 'repository_dispatch'
+      if: github.event_name == 'pull_request' || env.IS_PR_FROM_FORK
       run: docker pull "docker.pkg.github.com/${OWNER}/${DOCKER_CACHE_REPO}/${DOCKER_TAG}"
     - name: Tag docker image
-      if: github.event_name == 'pull_request' || github.event_name == 'repository_dispatch'
+      if: github.event_name == 'pull_request' || env.IS_PR_FROM_FORK
       run: docker tag docker.pkg.github.com/${OWNER}/${DOCKER_CACHE_REPO}/${DOCKER_TAG} ${DOCKER_TAG}
+    - name: Export commit range for fork PRs
+      if: env.IS_PR_FROM_FORK
+      run: |
+        echo "PR_COMMIT_RANGE=${{ github.event.client_payload.pull_request.base.sha }}...${{ github.event.client_payload.pull_request.head.sha }}" >> $GITHUB_ENV
     - name: Check pre-commit
-      if: github.event_name == 'pull_request' || github.event_name == 'repository_dispatch'
+      if: github.event_name == 'pull_request' || env.IS_PR_FROM_FORK
       run: |
         docker run \
           -e PR_COMMIT_RANGE \