Ensure CI works for both pull requests and pushes

.github/workflows/build.yaml

@@ -1,6 +1,10 @@
 name: Build firmwares
 
 on:
+  pull_request:
+    paths-ignore:
+      - '.gitignore'
+      - 'README.md'
   push:
     paths-ignore:
       - '.gitignore'
@@ -22,29 +26,17 @@ jobs:
           registry: ${{ env.REGISTRY }}
           username: ${{ github.repository_owner }}
           password: ${{ secrets.GITHUB_TOKEN }}
-      - name: Get current PR
-        id: get-current-pr
-        uses: 8BitJonny/[email protected]
-      - name: Read repository information (PR)
-        id: read-repo-info-pr
-        if: steps.get-current-pr.outputs.pr_found == 'true'
-        run: |
-          base_image=$(echo ${{ fromJSON(steps.get-current-pr.outputs.pr).base.repo.full_name }} | tr [:upper:] [:lower:])
-          head_image=$(echo ${{ fromJSON(steps.get-current-pr.outputs.pr).head.repo.full_name }} | tr [:upper:] [:lower:])
-          echo "base_image=$base_image" >> $GITHUB_OUTPUT
-          echo "head_image=$base_image" >> $GITHUB_OUTPUT
-      - name: Read repository information (no PR)
+      - name: Read repository information
         id: read-repo-info
-        if: steps.get-current-pr.outputs.pr_found == 'false'
         run: |
-          base_image=$(echo ${{ github.repository }} | tr [:upper:] [:lower:])
-          echo "base_image=$base_image" >> $GITHUB_OUTPUT
-          echo "head_image=$base_image" >> $GITHUB_OUTPUT
-      - name: Create container info
-        id: create-container-info
-        run: |
-          base_image="${{ steps.read-repo-info.outputs.base_image || steps.read-repo-info-pr.outputs.base_image }}"
-          head_image="${{ steps.read-repo-info.outputs.head_image || steps.read-repo-info-pr.outputs.head_image }}"
+          if $GITHUB_EVENT_NAME == 'pull_request'; then
+            base_image=$(echo ${{ github.event.pull_request.base.repo.full_name }} | awk '{print tolower($0)}')
+            head_image=$(echo ${{ github.event.pull_request.head.repo.full_name }} | awk '{print tolower($0)}')
+          else
+            base_image=$(echo ${{ github.repository }} | awk '{print tolower($0)}')
+            head_image=$(echo ${{ github.repository }} | awk '{print tolower($0)}')
+          fi
+
           tag_name="${{ hashFiles('Dockerfile') }}"
 
           # Default to building a new container under the original repo
@@ -57,10 +49,12 @@ jobs:
             build=false
           fi
 
-          # Check if we can use the head image (PR)
-          if docker manifest inspect ${{ env.REGISTRY }}/$head_image:$tag_name; then
-            image_name=$head_image
-            build=false
+          # Check if we can use the head image (if this is a PR)
+          if [[ $base_image != $head_image ]]; then
+            if docker manifest inspect ${{ env.REGISTRY }}/$head_image:$tag_name; then
+              image_name=$head_image
+              build=false
+            fi
           fi
 
           echo "build=$build" >> $GITHUB_OUTPUT