This commit introduces the `git branch` tool to the MCP Git server, allowing users to list branches with various filtering options.
Changes include:
- Implemented `git_branch` function in `src/git/src/mcp_server_git/server.py` to support listing local, remote, and all branches, as well as filtering by `contains` and `not_contains` SHA values.
- Added comprehensive unit tests for the `git branch` functionality in `src/git/tests/test_server.py`, covering different branch types and commit filtering scenarios.
- Updated `src/git/README.md`.
The git server currently lacks branch switching capabilities, limiting both
LLMs and developers. This adds branch checkout so LLMs can
help developers add new functionality in a new feature branch.