ci: Updated pull request workflow to run plan on changed config.

Author: jamesiarmes

.github/workflows/pull-request.yaml

@@ -4,13 +4,61 @@ on:
   pull_request:
 
 jobs:
+  configs:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout source code
+        uses: actions/checkout@v4
+      - name: Find all configs
+        id: find
+        uses: bendrucker/find-terraform-modules@v1
+        with:
+          working-directory: tofu/config
+      - name: Show all matching configs
+        shell: bash
+        run: |
+          mods=(${{ join(fromJSON(steps.find.outputs.modules), ' ') }})
+          printf "%s\n" "${mods[@]}"
+      - name: Find all changed files
+        id: diff
+        uses: technote-space/get-diff-action@v6
+        with:
+          FORMAT: json
+      - name: Show changed files
+        run: |
+          echo "${{ steps.diff.outputs.diff }}"
+      - name: Get the modified configs
+        id: modified
+        uses: actions/github-script@v7
+        with:
+          script: |
+            const configs = ${{ steps.find.outputs.modules }}
+            const diff = ${{ steps.diff.outputs.diff }}
+            const modifiedConfigs = configs.filter(
+              (config) => {
+                return !!diff.find(file => new RegExp(`^${config}/.+`).test(file))
+              }
+            )
+
+            core.setOutput('configs', modifiedConfigs)
+      - name: Show modified configs
+        run: |
+          echo "${{ steps.modified.outputs.configs }}"
+    outputs:
+      configs: ${{ steps.modified.outputs.configs }}
+
   plan:
     uses: ./.github/workflows/plan.yaml
+    needs: configs
     permissions:
       contents: read
       id-token: write
+    strategy:
+      matrix:
+        config: [ ${{ fromJson(needs.configs.outputs.configs) }} ]
     with:
       environment: development
+      config: ${{ matrix.config }}
     secrets:
       AWS_REGION: ${{ secrets.AWS_REGION }}
       AWS_ROLE_ARN: ${{ secrets.AWS_ROLE_ARN }}