Day 2: Bofs: BitKeeper

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Larry McVoy worked or probably more things that I know about, but he spent some time at Sun and SGI, and eventually created his own company: bitmover, to write a good source control system, because there are no really good ones available.

My favorite quote from him is if you ask him why CVS isn't good enough and why there is a need for bitkeeper, it's because you haven't used CVS for long enough and that you deserve to suffer with CVS for a while before you come back and ask how much bitkeeper is .

Bitkeeper is nearing completion, but it's not available for sale yet even though there are already a few beta sites.

In addition to my notes below, you can look at the BitKeeper slides on Larry's bitmover site

Let's start with the licensing idea, which I think it really brilliant: open source projects can use bitkeeper for free. Companies can use it without paying if they want to, but all their changelogs would sent to the openlogging.org web site for everyone to see, along with the Email address of the engineer who did the commit.
Since commercial companies will most likely not want their logs to go there, they get the option to pay for the commercial license: $800 for a small number of seats to $2600 for a big number (the richer you are, the more you pay). The cool thing is that everyone gets the same version of the software and that it encourages people to use open source. Everyone gets to use the software and pays what's appropriate.

Because one brilliant idea wasn't enough, the programmers in his company retain copyright of their code, so if the Bitmover company would "turn bad", the programmers can leave and create their own company to sell Bitkeeper. This is a good way to have check and balances. Don't you wish your manager were even half as clued and honest as that?
After enticing trust from his programmers, Larry also wants trust from his users, so if openlogging.org web site were to go down for more than 60 days, it would mean that the company is dead or doesn't care about the product anymore and then the bitkeeper source code would just become freely available to everyone.

Now, here are the main technical aspects of bitkeeper:

Support for changesets, which are patches on several files plus revision information. Change Sets are logical units of work, they record what was changed but also capture the entire state of the tree. Tagging is therefore immediate.
You check in your changes, but people can only see them once you do a commit which basically creates a changeset which contains all the diffs of all the files you changed since last commit. You can undo a commit and throw away all the code that you just added for the latest version.
Renames and symbolic links are logged, just like content
Bitkeeper supports multiple repositories
RCS and SCCS don't do a good job with lines of development. Bitkeeper is designed to handle them well, and especially lets you create a line of development after the fact on an old version.
Each work area has its own copy of the history, which allows disconnected operation (without a net connection or on a laptop).
When you create a bitkeeper project, it creates a unique ID which is used for tree syncing later. In case independant trees are created however, there is a way to merge them.
Bitkeeper contains wrappers to behave like RCS or SCCS depending on what the user prefers

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This is what Larry thinks of CVS/SCCS (Ok, this is a joke, but I had to find some reason to show this picture )

While I don't exactly remember the context of this picture, let's just say that Larry is a really cool fellow, outspoken, and fun to listen to.

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99/05/23 (10:58): Version 1.0