ct - change directories somewhere up in the hierarchy.

ct is a command line utility that quickly moves the current working directory from /a/foo/b/c/d to /a/bar/b/c/d. In principle, it is a shorthand for the operation cd ${PWD/foo/bar} which just replaces foo with bar in the current working path, but adds a few features such as autocompletion that are absolutely essential for a command line utility.