I use Subversion for this purpose. Super easy to set up and use on any modern non-windows OS. Also possible on windows but you'll need something like TortoiseSVN.
For example, I have a linux firewall, linux media server, linux on two RasPis, OSX on two MBPs and an imac. One SVN (Subversion) repository on one of the linux servers that holds all my code in a version controlled manner. I can push updates or check out revisions from any of the linux or OSX instances with a quick one-line command.
It might be a foreign concept right now but the learning curve is very small and once you start using it you'll wonder how you ever used multiple machines (and/or developers) to work on one project without it. Other options are CVS and git that basically do the same thing. CVS is antiquated and git is probably overkill, although the architecture of git is pretty cool and if yo uwant to stick your stuff on github, it's free and easy to use. You can also keep it private and local though if you want.