Tag Archives: mercurial

Get notifications about changes to any directory in mercurial

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Back in the old days when we used CVS of all things for our version control we had a wonderful tool called bonsai to help query the repository for changes. You could list changes on a per directory basis if you needed which was great for keeping an eye on certain chunks of code. I recall there being a way of getting an RSS feed from it and I used it when I was the module owner of the extension manager to see what changes were landed that I hadn’t noticed in bugs.

Fast forward to today and we use mercurial instead. When we switched there was much talk of how we’d get tool parity with CVS but bonsai is something that has never been replaced fully. Oh hgweb is decent at looking at individual files and browsing the tree, but you can’t get that list of changes per directory from it. I believe you can use the command line to do it but who wants to do that? Lately I’ve been finding need of those directory RSS feeds more and more. We’re now periodically uplifting the Add-on SDK repository to mozilla-central, it’s really important to spot changes that have been made to that directory in mozilla-central so we can also land them in our git repository and not clobber them the next time we uplift. I’m also the module owner of toolkit, which is a pretty big sprawling set of files. It seems like everytime I look I find something that landed without me noticing. I don’t make for a good module owner if I’m not keeping an eye on things so I’d really like to see when new files are added there.

So I introduce the Hg Change Feed, the result of mostly just a few days of work. Every 10 minutes it pulls new changes from mozilla-central and mozilla-inbound. A mercurial hook looks over the changes and adds information about them to a MySQL database. Then a simple django app displays that information. As you browse through the directories in the tree it shows only changesets that affected files beneath that directory. For any directory you can also get an RSS feed of the same. Plug that into IFTTT and you have an automated system to notify you in pretty much any way you’d like about new changes you’d be interested in.

Some simple examples. For tracking changes to Add-on SDK I’m watching http://hgchanges.fractalbrew.com/mozilla-inbound/file/addon-sdk/source. For toolkit I’m looking at http://hgchanges.fractalbrew.com/mozilla-inbound/file/toolkit?types=added. Types takes a comma separated list of “added”, “removed” and “modified” to filter which changes you’re interested in. There’s no UI on the site for changing that right now, you’re welcome to add some!

One other neat trick that this does is mostly ignore merge changesets. Only if a merge actually makes a change not already present in either of the merge parents (mostly happens when resolving merge conflicts) will it show up in the list of changes, because really you don’t need to hear about changes twice.

So play with it, let me know if you find it useful or if you think things are missing. I can also add other mercurial repositories if people want. Some caveats:

  • It only retains the last 2000 changesets from any repository in an effort to keep the DB size small and fast, it also only shows the last 200 changesets for each page, or just the last 20 in the feeds. These can be tweaked easily enough and I’ve done basically no benchmarking to say those are the right values.
  • The site isn’t as fast as I’d like, particularly listing changes for the top level directory takes nearly 5 seconds. I’ve thrown some basic caching in place to help alleviate that for now. I bet someone who has more MySQL and django experience than me could tell me what I’m doing wrong.
  • I’m off on vacation tomorrow so I guess I’m announcing this then running away, sorry if that means it takes me a while to respond to comments.

Want to help out and make it better? Go nuts with the source. There’s a readme that hopefully explains how to set up your own instance.

WebApp Tabs, version control and GitHub

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The extension I’ve been working on in my spare time for the past couple of weeks is now available as a first (hopefully not too buggy) release. It lets you open WebApps in Thunderbird, properly handling loading new links into Firefox and making all features like spellchecking work in Thunderbird (most other extensions I found didn’t do this). You can read more about the actual extension at its homepage.

Mostly I’ve been really encouraged during the development of this at just how far our platform has come for developing restartless add-ons. When we first made it possible in Firefox 4 there was a whole list of things that were quite difficult to do but we’ve come a long way since then. While there are still things that are difficult there are lots of things that are now pretty straightforward. My add-on loads simple XUL overlays, style overlays, installs JS XPCOM components with category manager registration, all similar to older add-ons. In fact I’m struggling to think of things that it is still hard to do though I’m sure other more prolific developers will have plenty of comments on that!

The other thing I’ve been doing with this extension is experimenting with git and GitHub. I think it’s been an interesting experience, there are continual arguments over which is better between git and mercurial with many pros and cons listed. I think most of these were done some time ago before mercurial and git really matured because from what I’ve seen there is really little difference between the two. They have slightly different default branching styles, but both can do the same kind of branching that the other can if you want and there are a few other minor differences but nothing that would really make me all that bothered over deciding which to use. I think the only place where git has a bonus is with GitHub, and really as far as I can see there isn’t a reason why someone couldn’t develop a similar site backed by mercurial repositories, it’s just that no-one really has.

GitHub is pretty nice with built-in basic issue tracking and documentation though it still has some frustrating issues. It seems odd for example that you can’t fork your own project, only someone else’s, but that’s only a minor niggle really. As project hosting goes I can’t say I’ve come across anything better that I can remember.