fix Build tag not being set correctly for deployments from prs (#684)

.github/workflows/pr.yaml

@@ -29,6 +29,10 @@ jobs:
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
           PR_NUMBER: ${{ github.event.issue.number }}
+      - name: Get the SHA of the current branch/fork
+        shell: bash
+        run: |
+          echo "SHORT_SHA=$(git rev-parse --short HEAD)" >> "$GITHUB_ENV"
         if: steps.trigger-deployment.outputs.triggered == 'true'
       - name: Set up Docker Buildx
         uses: docker/setup-buildx-action@v3
@@ -56,7 +60,7 @@ jobs:
           cache-from: type=gha
           cache-to: type=gha,mode=max
           build-args: |
-            BUILD_TAG=${{ github.sha }}
+            BUILD_TAG=${{ env.SHORT_SHA }}
       - name: Build and push worker Image
         if: steps.trigger-deployment.outputs.triggered == 'true'
         uses: docker/build-push-action@v6
@@ -69,7 +73,7 @@ jobs:
           cache-from: type=gha
           cache-to: type=gha,mode=max
           build-args: |
-            BUILD_TAG=${{ github.sha }}
+            BUILD_TAG=${{ env.SHORT_SHA }}
       - name: Deploy if triggered
         if: steps.trigger-deployment.outputs.triggered == 'true'
         env: