iterative committing

A few weeks ago, I saw this interesting complaint about distributed revision control advocacy:

But really, to read some of these articles, you'd think 99.9% of OSS contributions come from people who live on planes, only get 10% uptime on their broadband at home, and are incapable of spending the five minutes required to install something like Subversion locally for use with side projects.

This particular complaint resonated with me because I've always had a slight feeling that all this talk of airplanes and intermittent online access is missing the point.

I think what would help these discussions is to introduce the idea that there are really two ways to be disconnected: the involuntary way that most people talk about, and the voluntary way which is the really interesting one.

To be involuntarily disconnected is to be literally or technically offline. The universe prevents you from phoning home because it broke your wifi card or plunked you deep in an Amazonian rain forest. True, a distributed revision control system lets you continue hacking in the face of such adversity; but this fact isn't very convincing to some folks who are used to centralised revision control. How often in today's world are you really involuntarily offline? The trick is that sometimes your disconnectedness is entirely voluntarily. I don't really mean that in the sense of unplugging your cable modem and calling a moratorium on network access for the day. The minute you want to commit to a server and can't because of missing network access, you are offline involuntarily, even if this came as the result of a voluntary decision.

What I mean is that distributed revision control allows you to have pockets of deliberate disconnectedness from your peers. You want to work on something in little bits and pieces, you want to version control your work in progress, but you don't want to inflict your uncompleted work on your friends. A distributed VCS gives you a chance to step back for a moment and continue working with the benefit of version control. There are two alternatives to stepping back, neither of which are really acceptable. The first is to go ahead and commit your stuff with wild abandon, the consequences of which being that you pollute the change history with unfinished work and make life potentially difficult for your friends. The second alternative is NOT to commit your stuff at all, the consequences of which being that you lose the ability to track and log your your work as you go along.

A distributed revision control system gives you the choice of iterative committing. It doesn't really matter if you are online or offline actually. Sometimes you just want to commit something for your own sake and only later decide if the commits should be shared with the main repository or not. In the meantime you can choose to go back, undo a commit, redo a commit, undo all your intermediary commits and lump them all into one big commit, update from the main repository and then rework your commit in the new context. These are the choices that a distributed revision control system offers.

It's heartening to see that the idea of using a distributed VCS is catching on, that people are starting to adopt the likes of darcs, git, mercurial and bzr for their work. It means that the joy of iterative committing is spreading. Of course, I am partial to one of these systems in particular. Perhaps in a future article, I can describe what I think is the essential difference between darcs and our estimable competitors. I think I will call it iterative merging.

Happy committing in the meantime!