With GIMP's "Map to sphere"A few years ago, while I was still mainly a Windows user, I read 'Pragmatic programmer: From journeyman to master', and learnt about Version Control Systems. You know, SVN, CVS, Git, Darcs. As I was just a single user working locally (just wanted the incremental and logged backups), I installed RCS. Almost the oldest, and in some sense the most simple. It can work