My local repos were full of zombie branches and git never told me which ones were safe to delete

Last week, the author ran the command 'git branch' in one of their older working directories and was overwhelmed by the sheer number of local branches listed - forty-some. This clutter was not a concern for disk space, but rather it made other git commands less efficient. Git log --all became noisy, tab completion for branch names stopped working, and the task of pruning became a daunting prospect, as deleting a branch that was thought to be dead could lead to a headache weeks later when a commit was needed.

The author attempted the usual methods, such as using git branch --merged main, but it also listed the current branch and deleting a branch based on the output could lead to disastrous consequences. Another method, git branch -vv, showed [gone] for branches whose upstream had vanished, but it required manual interpretation of the output.

No single command provided reasons per branch, which led the author to create a Python script named git-stale. This tool, consisting of a 5,092-byte single file, imports four modules from Python's standard library and runs without any additional installations. The core functionality of the script checks if a branch is merged into the default branch, if its upstream branch no longer exists, or if its last commit is older than a specified threshold.

The script uses a thin wrapper-over-git approach, asking git itself to determine the truth, rather than introducing potential bugs by attempting to replicate merge-base logic or parse the index.