Task/issue tracking system with command-line interface

Ditz is a simple, light-weight distributed issue tracker designed to work with distributed version control systems like darcs and git.

Ditz: http://web.archive.org/web/20121212202849/http://gitorious.org/ditz

Also cloned here: https://github.com/jashmenn/ditz

Interesting idea; the closest thing I have heard of is todo.txt.

Alternatively, you could roll your own by just using a database (e.g. sqllite) and SQL. Optionally, write a wrapper script that parses your plain-text file and command-line options, and generates the corresponding SQL.