workflows/lint: add clang-format on changed files

The entire codebase is not ready to be clang-formatted and probably
never will be, but we can at least check if the changes in new pull
requests follow our coding style.

.clang-format

@@ -0,0 +1,38 @@
+---
+Language: Cpp
+BasedOnStyle: Google
+IndentWidth: 4
+PPIndentWidth: 1
+IndentPPDirectives: AfterHash
+IndentCaseLabels: false
+IncludeBlocks: Preserve
+SortIncludes: true
+SpaceAfterCStyleCast: false
+AllowShortIfStatementsOnASingleLine : Never
+AllowShortLoopsOnASingleLine: false
+AllowShortFunctionsOnASingleLine: false
+AlignConsecutiveMacros: true
+AllowAllArgumentsOnNextLine: false
+AllowAllParametersOfDeclarationOnNextLine: false
+Cpp11BracedListStyle: false
+InsertNewlineAtEOF: true
+SpacesInContainerLiterals: false
+BinPackArguments: true
+BinPackParameters: true
+AlignAfterOpenBracket: Align
+BracedInitializerIndentWidth: 4
+SeparateDefinitionBlocks: Always
+BreakBeforeBraces: Custom
+AllowShortCaseLabelsOnASingleLine: true
+BraceWrapping:
+  AfterControlStatement: MultiLine
+  AfterCaseLabel: false
+  AfterEnum: true
+  AfterFunction: true
+AlignConsecutiveAssignments:
+  Enabled: true
+  AcrossEmptyLines: false
+  AcrossComments: false
+PackConstructorInitializers: Never
+BreakConstructorInitializers: BeforeComma
+---

.github/workflows/lint.yml

@@ -46,3 +46,15 @@ jobs:
       - uses: actions/checkout@v4
       - uses: editorconfig-checker/action-editorconfig-checker@main
       - run: editorconfig-checker -config .editorconfig-checker.json
+
+  clang-format-lint:
+    runs-on: ubuntu-latest
+    container:
+      image: "registry.opensuse.org/home/mia/images/images/mpv-ci:stable-deps"
+    if: github.event_name == 'pull_request'
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 50
+      - name: Check Formatting
+        run: git clang-format ${{ github.event.pull_request.base.sha }} --diff