`.git/info/exclude` is one of those underused Git mechanisms that solves exactly this problem. Per-repository local ignores without touching the shared `.gitignore`. The point about AI coding tools (Claude Code, Cursor, etc.) respecting git's ignore state is the genuinely useful angle here: hiding personal prompt files and context notes means they don't pollute the assistant's context window when it indexes the project. Nice quality-of-life tool for teams where AI-assisted development has become standard.