Encapsulating this action into a custom action fails with run-clang-format.py: error: No files found

[mwestphal]

When creating an action using this action like this:

name: 'Style Checks'
description: 'Perform Style Checks'
inputs:
  source_directory:
    description: 'Existing git directory to perform style checks on'
    default: '.' 

runs:
  using: "composite"
  steps:

    # Run codespell first to avoid issues with style check on same location
    - name: Codespell in place
      shell: bash
      run: |
        pip install codespell
        codespell -fHw ${{ inputs.source_directory }}

    - name: C++ Formatting
      uses: DoozyX/clang-format-lint-action@v0.16
      with:
        source: ${{ inputs.source_directory }}
        extensions: "h,cxx,in"
        exclude: "./cmake **/*.py.in **/*.log.in **/*.json.in **/*.thumbnailer.in **/*.cmake.in **/*.desktop.in"
        clangFormatVersion: 18
        inplace: True

...

Our CI fails with:

run-clang-format.py: error: No files found

Job:

https://github.com/f3d-app/HelloWorld/actions/runs/20259877155/job/58169631446