Add CONTRIBUTING.md

CONTRIBUTING.md

@@ -0,0 +1,72 @@
+# How to Contribute
+
+We welcome community contributions to OAR. Thank you for your time! By
+contributing to the project, you agree to the license, patent and copyright
+terms in the AOM License and Patent License and to the release of your
+contribution under these terms. See [LICENSE](LICENSE) and [PATENTS](PATENTS)
+for details.
+
+## Contributor License Agreement
+
+In order to contribute, you must execute the appropriate
+[Contributor License Agreement](https://aomedia.org/about/legal/#contributor-license-agreements)
+to ensure that AOMedia has the right to distribute your changes.
+
+## Coding style
+
+We are using the style defined by the
+[Google C++ Style Guide](https://google.github.io/styleguide/cppguide.html) as
+applied to C, enforced with clang-format using the
+[.clang-format](.clang-format) configuration file in the root of the
+repository.
+
+The bundled Open Binaural Renderer (obr) library at
+[src/renderer/obr/obr_capi/obr](src/renderer/obr/obr_capi/obr) carries its own
+[.clang-format](src/renderer/obr/obr_capi/obr/.clang-format) configuration.
+Since clang-format applies the configuration file nearest to each source file,
+the command below formats files in both trees correctly.
+
+```sh
+# Apply clang-format to modified .c, .h files
+clang-format -i --style=file \
+  $(git diff --name-only --diff-filter=ACMR '*.c' '*.h')
+```
+
+## Contribution process
+
+- Validate that your changes do not break the build, locally and through the
+  GitHub Actions CI:
+
+  ```sh
+  cmake -S . -B build -DOAR_BUILD_EXAMPLES=ON
+  cmake --build build
+  ```
+
+- Run the example programs as smoke tests and ensure they pass:
+
+  ```sh
+  ./build/tests/examples/test_audio_element_types
+  ./build/tests/examples/test_channel_based_rendering
+  ./build/tests/examples/test_scene_based_rendering
+  ./build/tests/examples/test_object_based_rendering
+  ```
+
+- Run the obr unit tests and ensure they pass:
+
+  ```sh
+  ctest --test-dir build/src/renderer/obr/obr_capi/obr -L obr --output-on-failure
+  ```
+
+- Submit a pull request for review by the maintainers.
+
+## Pull request process
+
+- Authors should use a valid email account when committing.
+- Make clear and concise commits (one commit per feature or issue).
+- Authors are responsible for breaking down the pull request into sensible
+  commits with proper commit messages.
+- Avoid using force push when addressing comments and review items.
+- Maintainers shall use 'rebase and merge' to make sure all commits can apply
+  cleanly onto the main branch.
+- Maintainers shall only use 'squash and merge' with the permission of the
+  authors.