ci: clang_format.yml lints only modified source files (#196)

closes #128

.github/workflows/clang_format.yml

@@ -24,10 +24,31 @@ jobs:
           # make sure the parent commit is grabbed as well, because
           # that's what will get formatted (i.e. the most recent commit)
           fetch-depth: 2
+      # retrieve comma-separated list of modified files
+      - name: Retrieve changed files
+        id: changed-files
+        uses: tj-actions/changed-files@v42.0.5
+        with:
+          files: |
+            src/**/*.{cpp,h}
+            include/**/*.{h,hpp}
+            **/*.hlsl
+            **/*.hlsli
+          separator: ","
+        # process modified files list before passing to clang-format-lint-action
+      - name: Process changed files list
+        id: process-list
+        run: |
+          CHANGED_FILES="${{ steps.changed-files.outputs.all_changed_files }}"
+          CHANGED_FILES="${CHANGED_FILES// /\\ }"
+          CHANGED_FILES=$(echo "$CHANGED_FILES" | tr ',' ' ')
+          echo "::set-output name=changed_files::${CHANGED_FILES}"
       # format the latest commit
-      - uses: DoozyX/clang-format-lint-action@v0.16.2
+      - name: Format changed files
+        if: steps.changed-files.outputs.any_changed == 'true'
+        uses: DoozyX/clang-format-lint-action@v0.17
         with:
-          source: "."
+          source: "${{ steps.process-list.outputs.changed_files }}"
           exclude: "extern include"
           extensions: "h,cpp,c,hlsl,hlsli"
           clangFormatVersion: 16