A custom prompt for zsh.
A list of "links" and a program to manage them.

Links == symlinks, or similar, that link into dotfiles. (e.g., .vimrc
links to the "vimrc" in the dotfiles repo.)
Code to deal with shell file "links".
Use helper functions.
Make "manage" a Python package, move functionality to it.

Move the "abort_with_error" helper into manage/, make manage/ a real
Python package, stop hacking around with sys.path.