Re: [TUHS] PWB contributions

On Sun, Nov 08, 2015 at 08:39:12PM -0500, Doug McIlroy wrote: Marc Rochkind did SCCS, right? Wikipedia said he did it at Bell Labs. Does anyone on the list remember him? I'd love to hear some stories about how SCCS was created. Warning: source management rant coming. SCCS got a bad rap from Walter Tichy when he created RCS, I can't remember his dislike but it's completely wrong. RCS is diff based, you have a file and a series of patches. For the tip of the trunk, that's the file, going backwards in history they are reverse patches. OK, not so crazy. But now think about a branch. You do reverse patches back to the branch point and forward patches down to the tip of the branch. Anyone living on a branch hated RCS. SCCS has interleaved deltas. It's a brilliant design that has far far better performance than anything else out there. I'll explain that if anyone cares but I'd love to know if anyone talked to Marc while he was building SCCS. Love to learn how he came up with that. The reason I know so much about SCCS is that BitKeeper is sort of SCCS on steroids, we took the file format, fixed a bunch of stuff, and made the first distributed version control system with it. Git, Mercurial, all the others, are copies of what we did. I wish Marc was on this list, be fun to chat. --lm