***Added:***
- Add ability to select specific environments for command execution of matrices based on variables
- Support a `HATCH_PYTHON` environment variable that, for example, environments may use before defaulting to the Python executable Hatch is running on
- Also use the `SHELL` environment variable fallback on Windows systems
- Update project URLs metadata
hatchling-v0.21.0
***Changed:***
- In order to simplify configuration, metadata hooks are now configured under `tool.hatch.metadata.hooks` rather than directly under `tool.hatch.metadata`
***Added:***
- Add option to allow the use of direct references for dependencies
- Make the default pattern for the `regex` version source case insensitive
- Deduplicate and normalize dependency definitions before writing metadata for wheels and source distributions
- Normalize the names of optional dependency groups to adhere to the newly-introduced [PEP 685](https://www.python.org/dev/peps/pep-0685/)