git-sizer is an open-source tool designed to help developers manage and optimize Git repositories by providing size metrics and identifying potential issues related to repository structure and content. It assesses various properties of a Git repository, such as the number of objects, uncompressed size, number of commits, and references, which can affect performance even if the overall disk usage isn't excessive. By analyzing these factors, git-sizer helps users understand if their repository is pushing Git's limits, potentially causing slower operations, and suggests improvements for better efficiency. The tool is particularly useful when setting up a repository or migrating from another version control system, where establishing good practices early can prevent future complications. The Linux kernel is cited as an example of a large but well-balanced repository that operates efficiently within Git's capabilities. Users are encouraged to engage with the git-sizer project by reporting bugs or contributing to its development.