To The Point Of Collapse

Oh GNOES! SCM DISCUSSIONZ0R!!!!!!
After seeing everyone shill for their favorite scm lately, with most of the predictable ones getting the attention, I thought I'd throw my choice out there, just to see it represented.

I primarily use svn with my work on X in Debian, and it's a wonderful system. Fortunately though, I don't have to maintain the repos, and when something goes wrong I can cry to our beloved DPL to get his admin on, and he fixes things up. This works out fairly well for me as a basic user, but I don't want to be dealing with these sorts of hassles for smaller projects. The distributed scm thing appealed to me in this sense, so when arch started to become a serious buzzword in the Debian crowd I had a look.

Well, more than a look. I fought for over a month with tla and baz and found that they were both so unuseable and poorly documented that I couldn't do more than scream and cry. bzr looked cool, but it wasn't ready (I sorta tried to manage one of the X.Org releases in Debian with it and failed miserably). Darcs was slow and in a minority language, which was a major turnoff for me. And I don't have a ton of diskspace, so git was out. Svk struck me as a hack (it still does) so I didn't want to go with that. Monotone was ok, but not good enough, so I sighed, gave up, and went back to svn thinking that this was as good as it could get. Indeed, we added a quilt-based patch system to the Xorg packages, so now I have a mini-scm (quilt) inside an scm (svn) and it works amazingly well.

But one of my friends just got hired by the people who make Xen, and he mentioned that they used mercurial, and asked if I had tried it yet. I scoffed and said no, and that all scm's suck harder than anything has ever sucked before, but I had a lot of time to kill while I was waiting on an X build, so I gave it a look.

Mama, I'm home. I was stunned that I was able to pick up mercurial in about half an hour after tearing my hair out for over a month with arch.

The UI is apparently very darcs-like (by accident, according to the mercurial author) which is known to be fantastic. Branching, merging, etc is simple as can be so far, although upstream is still working out better methods to deal with merging.

It's very fast, built for large trees (i.e. the kernel) so it will be suitable for managing X with (although I haven't tried this yet, but I plan to). For X, I'll need something fast to keep my sanity. This rules out darcs and baz (which has somehow managed to get amazingly slow in addition to being difficult as of late).

Unlike git, it keeps changesets in xdelta format rather than storing whole files, so it doesn't eat my hard drive.

It's written in python, so it's something I could hack on if I want to.

It supports an easy server setup with apache, and you can push your repos and serve them via static http if you don't have a server, like me.

Like monotone, it exposes hashes to the user, but unlike monotone it also provides a local revision number to make sure you don't spend all your time copying and pasting hashes, which is what put me off from monotone.

It has a fairly small command set, with 39 commands in the current tip (i.e. HEAD) as opposed to the > 150 in baz which made me weep.

It feels like using bzr, except it's here now and ready for production. Indeed, it's already used in production in making Xen.

There's a bunch more that I won't talk about, mainly because these are the things that have grabbed me. A note of caution is that I've only been hacking on local projects by myself (mainly configure-debian) with it, so I don't have the tons of real world experience with multiple trees that the thing is built for yet. I'm thinking about putting up a parallel mercurial tree to the XSF tree just for fun (the svn repo would remain the canonical one) if people are interested and I can find a server. I hope though, that all the people out there who, like me, were bouncing around trying out scm after scm and never being quite happy with any of them at least give mercurial a fair chance. I'm still amazed at how much I like it, and I think some others might feel the same.

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