Like others, I wrote a tool to manage "layers" of configuration and personalization files (https://github.com/dcreemer/wsup). "wsup" lets me compose various work configurations, personal dotfiles (https://github.com/dcreemer/dotfiles), dot-emacs files (https://github.com/dcreemer/dotemacs) and others from multiple git repositories.
The project was born from my need to manage multiple changing personal and work environments. Now I can go from zero to full environment with a couple of commands.