Because it's a direct screen capture from Google Trends, and for me, it's pretty clear which are they: CVS, SVN, Hg, Git. Here, I've re-created it for you: http

Because it's a direct screen capture from Google Trends, and for me, it's pretty clear which are they: CVS, SVN, Hg, Git. Here, I've re-created it for you: https://www.google.com/trends/explore?date=all&q=%2Fm%2F05vqwg,%2Fm%2F012ct9,%2Fm%2F08441_,%2Fm%2F09d6g https://www.google.com/trends/explore?date=all&q=%2Fm%2F05vq...