Undo non-sparse checkout. Try using refs syntax for master commit

.github/workflows/ci.yml

@@ -12,10 +12,6 @@ jobs:
     runs-on: windows-latest
     steps:
       - uses: actions/checkout@v4
-        with:
-          # Force a non-shallow checkout, so that clang-format can access source history to compare against
-          # See https://github.com/actions/checkout for more details.
-          fetch-depth: 0
 
       - name: Find vcvars64.bat
         run: |
@@ -34,7 +30,7 @@ jobs:
             exit /b %ERRORLEVEL%
           )
 
-          git clang-format master --binary "%CLANG_FORMAT%" --style file -- cppwinrt/*.h cppwinrt/*.cpp fast_fwd/*.h fast_fwd/*.cpp prebuild/*.h prebuild/*.cpp scratch/*.h scratch/*.cpp strings/*.h strings/*.cpp test/*.h test/*.cpp vsix/*.h vsix/*.cpp
+          git clang-format refs/remotes/origin/master --binary "%CLANG_FORMAT%" --style file -- cppwinrt/*.h cppwinrt/*.cpp fast_fwd/*.h fast_fwd/*.cpp prebuild/*.h prebuild/*.cpp scratch/*.h scratch/*.cpp strings/*.h strings/*.cpp test/*.h test/*.cpp vsix/*.h vsix/*.cpp
 
           if %ERRORLEVEL% neq 0 (
             echo ::error::This branch contains changes that have not been formatted with 'clang-format',