Covers arg parsing, version comparison, audit phase (git config,
signing, SSH), apply phase (settings, SSH directives, url rewrite),
signing key detection (standard/custom/tilde/sk-preference),
allowed signers, -y mode, backup, and end-to-end idempotency.
All tests run in isolated HOME to avoid touching real config.
Closes: #6🤖 Generated with [Claude Code](https://claude.ai/code)
Co-Authored-By: Claude <noreply@anthropic.com>
