Here are some reasons why a pull request may not be merged:
- It hasn’t been reviewed.
- It doesn’t include specs for new functionality.
- It doesn’t include documentation for new functionality.
- It changes behavior without changing the relevant documentation, comments, or specs.
- It changes behavior of an existing public API, breaking backward compatibility.
- It breaks the tests on a supported platform.
- It doesn’t merge cleanly (requiring Git rebasing and conflict resolution).