Update Docker updater workflow (nginx#2679)

Fixed a few issues in the workflow, mainly the build step that had a wrong if (all the outputs are strings).
Also added an option to force the update.

Author: miledxz

.github/workflows/build.yml

@@ -27,7 +27,7 @@ jobs:
       security-events: write # for github/codeql-action/upload-sarif to upload SARIF results
       packages: write # for docker/build-push-action to push to GHCR
       id-token: write # for docker/login to login to NGINX registry
-    runs-on: ${{ github.event_name != 'pull_request' && contains(inputs.image, 'plus') && 'kic-plus' || 'ubuntu-22.04' }}
+    runs-on: ${{ github.event_name != 'pull_request' && contains(inputs.image, 'plus') && 'kic-plus' || 'ubuntu-24.04' }}
     services:
       registry:
         image: registry:2
@@ -101,6 +101,7 @@ jobs:
         id: meta
         uses: docker/metadata-action@8e5442c4ef9f78752691e2d8f8d19755c6f78e81 # v5.5.1
         with:
+          context: ${{ inputs.tag != '' && 'git' || 'workflow' }}
           images: |
             name=ghcr.io/nginxinc/nginx-gateway-fabric,enable=${{ inputs.image == 'ngf' && github.event_name != 'pull_request' }}
             name=ghcr.io/nginxinc/nginx-gateway-fabric/nginx,enable=${{ inputs.image == 'nginx' && github.event_name != 'pull_request' }}

.github/workflows/update-docker-images.yml

@@ -3,7 +3,12 @@ name: Update Docker Images
 on:
   schedule:
     - cron: "0 2 * * *" # run every day at 02:00 UTC
-  workflow_dispatch:  # yamllint disable-line rule:empty-values
+  workflow_dispatch:
+    inputs:
+      force-update:
+        description: 'Force update of images'
+        required: false
+        type: boolean
 
 defaults:
   run:
@@ -43,15 +48,15 @@ jobs:
       - name: Set NGINX version
         id: nginx
         run: |
-          version=library/nginx:$(grep -m1 "FROM.*nginx:.*alpine" < build/Dockerfile.nginx | awk -F"[ :]" '{print $3}')
+          version=$(grep -m1 "FROM.*nginx:.*alpine" < build/Dockerfile.nginx | awk -F" " '{print $2}')
           echo nginx_version=${version} >> $GITHUB_OUTPUT
 
   check:
     name: Check if updates are needed
     runs-on: ubuntu-24.04
     needs: variables
     outputs:
-      needs-updating: ${{ steps.needs.outputs.needs-updating }}
+      needs-updating: ${{ steps.update.outputs.needs-updating }}
     steps:
       - name: Login to GitHub Container Registry
         uses: docker/login-action@9780b0c442fbb1117ed29e0efdff1e18412f7567 # v3.3.0
@@ -66,15 +71,11 @@ jobs:
         with:
           base-image: ${{ needs.variables.outputs.nginx_version }}
           image: ghcr.io/nginxinc/nginx-gateway-fabric/nginx:${{ needs.variables.outputs.ngf_tag }}
-          platforms: "linux/arm64,linux/amd64"
-
-      - id: needs
-        run: echo "needs-updating=${{ steps.update.outputs.needs-updating }}" >> $GITHUB_OUTPUT
 
   build:
     name: Build Image
     needs: [variables, check]
-    if: ${{ needs.check.outputs.needs-updating }}
+    if: ${{ needs.check.outputs.needs-updating == 'true' || inputs.force-update == true }}
     uses: ./.github/workflows/build.yml
     with:
       image: nginx