.github/workflows/editorconfig.yml: use api for list of changed files

faster than doing a full clone and using git diff

.github/workflows/editorconfig.yml

@@ -8,13 +8,22 @@ on:
 jobs:
   tests:
     runs-on: ubuntu-latest
+    if: github.repository_owner == 'NixOS'
     steps:
+    - name: Get list of changed files from PR
+      env:
+        GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+      run: |
+        echo 'PR_DIFF<<EOF' >> $GITHUB_ENV
+        gh api \
+          repos/NixOS/nixpkgs/pulls/${{github.event.number}}/files --paginate \
+          | jq '.[] | select(.status != "removed") | .filename' \
+          >> $GITHUB_ENV
+        echo 'EOF' >> $GITHUB_ENV
     - uses: actions/checkout@v2
-      with:
-        fetch-depth: 0
-    - uses: technote-space/get-diff-action@v4.0.0
+      if: env.PR_DIFF
     - name: Fetch editorconfig-checker
-      if: env.GIT_DIFF
+      if: env.PR_DIFF
       env:
         ECC_VERSION: "2.2.0"
         ECC_URL: "https://github.com/editorconfig-checker/editorconfig-checker/releases/download"
@@ -23,7 +32,6 @@ jobs:
         tar xzf ec-linux-amd64.tar.gz && \
         mv ./bin/ec-linux-amd64 ./bin/editorconfig-checker
     - name: Checking EditorConfig
-      if: env.GIT_DIFF
+      if: env.PR_DIFF
       run: |
-        ./bin/editorconfig-checker -disable-indent-size \
-        ${{ env.GIT_DIFF }}
+        echo "$PR_DIFF" | xargs ./bin/editorconfig-checker -disable-indent-size