Terry Jones

A year ago we switched from SVN to Bazaar for source code control. I started using source code control in 1989 with RCS after comparing it with SCCS. Then I duly moved to CVS and on to SVN. In retrospect, they all sucked pretty badly but each in turn was a big improvement and seemed great at the time.

The topic of source code control is a very complex one. There’s tons of debate online about the advantages of various packages. I don’t want to get into details, plus there are details that I don’t fully appreciate anyway. It really is complex – at least if you want to do anything even a little bit sophisticated, e.g., with multiple users working on multiple branches.

Anyway, we wanted to move away from SVN, which is cumbersome, too manual and heavyweight (at least in its handling of branches), and requires you to talk to a centralized server all the time. Plus it has no handling of directories or symbolic links, and you lose history in merging. There are other problems and annoyances too.

A distributed version control system seemed like the way to go.

We looked closely at Bazaar and Mercurial. I was prejudiced towards Mercurial. I liked its name, I liked the coolness of the Qwerty-symmetric hg command, and above all I liked how lightweight and simple it is. We took a quick look at Git, but it looked like a bit of a hodge-podge and we’re Python fanboys, so we fairly quickly decided against it.

From what I’ve read, all of Bazaar, Mercurial and Git are excellent. It’s clear that they leave SVN for dead. When I run across open source projects, especially new projects, that are still using SVN I silently raise an inner eyebrow.

But like I said, I don’t want to get into details. What I do want to do is say that I really like a plugin for Bazaar called viz (aka vizualize). It’s in bzr-gtk in case you use apt-get.

You just type bzr viz and it pops a glorious window with a visualization of your branching and merging history. The image above is just a fragment of the full window. The most recent activity is at the top, so as you look down the page you’re looking at older and older branches and merges. On the left you see the branch numbers. The vertical lines are the branches, the left-most being the trunk (in this case). You can see that the 2 right-most branches have no activity in the fragment shown.

If you want to take a look at more of the window, showing a different part of the tree, click on the following image.

Not only does Bazaar make branching really lightweight, it takes all the uncertainty out of the process (ever try merging branches in SVN, reading the log file to make sure you’ve got the right revision numbers before entering the extremely long command?). Plus you get full history when merging (and this is nicely displayed in the output of bzr log) and with a tool like bzr viz you can just see the history. Our tree has some much more complex sections, including one where Esteve had 25 branches going at the same time! And yes, they all got merged to trunk. Bazaar makes branching and merging so simple you just start to do it all the time, and it becomes very natural. Then you just merge whatever you like into whatever you like and gradually merge your way back into the trunk (after merging the trunk into your branch first to have a look at things). It’s great.

That’s it. No time for blogging. I’m waiting for someone to upload a patch so I can continue working. Meanwhile, lightweight distributed version control has really changed how we work. It’s much much better. If you’re still using SVN and haven’t checked out Bazaar or Mercurial (and there are several others), you really should.

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