[dnr]

Here's my solution: https://bitbucket.org/davidn/dotstuff

Briefly: ~/dotstuff is a hg/git/whatever repo that contains your dotfiles, which can optionally use simple preprocessor directives to turn on or off different sections on different systems, or contain macro substitutions. You run 'dot' and it shows you a diff between what's in the repo and what's in your filesystem. Then run 'dot -g' to make the changes (with optional backups). Also manages crontabs.

I wrote it about four years ago and have been using it happily since then to manage dotfiles on 2-4 different systems. (I wrote the README today before posting this, which is why it has today's date.)