svnmerge, a tool to manage SVN merges

We use SVN on a project with a lot of small branches, i.e. a branch for almost every non-trivial feature. This is not a particularly pleasant want to use SVN, but it meets another important need for our project: code review on the way in to the trunk (as a “gate”), rather than code review for code already in trunk (“drive-by” code review).

Today on the XPSTL mailing list, Mike Jorgensen pointed me to svnmerge:

“ is a tool for automatic branch management. It allows branch maintainers to merge changes from and to their branch very easily, and automatically records which changes were already merged. This allows displaying an always updated list of changes yet to be merged, and totally prevents merge mistakes (such as merging the same change twice).”

svnmerge looks rough, but should still be a big improvement of SVN alone. It’s a ways short of what’s in the box with git, bzr, etc., but is also a much smaller step for a team using SVN.

Speaking of merging, Mark Shuttlework recently argued merging is the key to software developer collaboration. To me, this is obviously true, and not only for open-source projects, but for closed-source projects also.  If it sounds untrue to you, then you and I are probably thinking of different meanings of “merge”.

Next Big Language = JavaScript

There’s a lot of buzz about Steve Yegge’s “port” of Rails to JavaScript, and Steve has now provided (in his funny, self-deprecating style) the background of how it came to be. He doesn’t quite say it explicitly in this post, but I think it reveals that the “Next Big Language” he has been hinting at is JavaScript.

I (mostly) agree:

JavaScript is in nearly every browser, including tiny ones (like the one in my BlackBerry Pearl). It may be the single most widely available language today.

Because of the above, an enormous population of JavaScript programmers (though sometimes of dubious skill) has emerged.

Starting with Java 6 it’s “in the box” there also. To me, this makes it the likely winner, by a wide margin, for a dynamic language to be used at Java shops or inside Java projects. Being “in the box” is a powerful advantage, one which the many other contenders will have a hard time overcoming.

Adobe’s new JavaScript virtual machine implementation, which they handed over to Mozilla as “Tamarin”, sounds like it will boost JavaScript performance great, making it good enough for a very wide variety of projects.

JavasScript uses curly braces, like the last few Big Languages.

Like Java, C, C++, etc., JavaScript has specs and multiple competing, complete, current, high quality implementations. This, to me, is a big advantage over Ruby, Python, and other currently popular dynamic languages. Of course there is plenty of room in the industry for these language to thrive also, I am not saying any of them will go away; we use Python with great results and expect to keep doing so.
Mark Volkmann initially thought I was nuts to predict JavaScript as a winner but came around a few month later (and said so in a user group talk).

In a project at work, we’d adopted JavaScript as our plugin extension language for user-customizable rules (billing rules, etc.). I’d have chosen Lua (as I did for another project), but there are at least 1000x as many JavaScript programs out there. So far it has worked very well. If we had it to do over we might implement far more of the project in JavaScript.

However, there are a few reasons why I only “mostly” agree:

First, with JavaScript there isn’t a good way to avoid shipping source code. Sure, you an obfuscate JavaScript with various tools, but the results remains far for amenable to readable-source recovery than in a more traditionally compiled language. For open source projects this is no big deal, but there are also many worthwhile businesses and projects which depend on proprietary, not open software (including most of our projects), and it’s not year clear that obfuscation is sufficient protection. (Update in reply to a comment below: This matters even for server-side software, because some of us create and sell software products for other people to run on their servers.)

Second, at the moment JavaScript appears to lack a module system, without which it’s painful to build large systems. I expect an upcoming language version will address this.

synsync: another way to remotely backup / svnadmin dump an SVN repository

Last month, I described an approach using SVK to remotely clone and then “svnadmin dump” an SVN repository. It turns out that there is an easier way “in the box” in SVN 1.4: the svnsync tool. Bob Ippolito describes how to do it, here are the minimal steps:

$ MYREPO=/home/me/someplace    (do not use ~username, use /home/username)
$ svnadmin create $MYREPO
$ echo “#!/bin/sh” >$MYREPO/hooks/pre-revprop-change
$ chmod +x $MYREPO/hooks/pre-revprop-change
$ svnsync init file://$MYREPO
$ svnsync sync file://$MYREPO

… then repeat the “svnsync sync” to sync down the changes since last time, perhaps in a cron job.

Paul Querna describes some caveats, and Cheah Chu Yeow offers a longer walkthrough of a more “produciton-grade” svnsync setup.

Like the SVK approach, with synsync you get a local mirror of a remote repo, with no need for shell access to that repo – very helpful if the repo is hosted by, for example, a SVN hosting firm, SourceForge, or Google Code. This local mirror can be used to view project history without network access, to svnadmin dump for backups, to mirror efficiently in another source control tool (I’m doing this with git as a test now, for one of our projects), etc.