Mercurial and Eclipse

I’m not opposed to using the command line. Some times it’s the best way to get things done. But when it comes to source control I think having good IDE integration really helps with productivity. I’ve been in situations before where there wasn’t good integration, and, though you can certainly get things done like that, I end up fighting with the VCS more often. I think this is especially true when you are working in a team.

So one of the first things I want to know when looking at a VCS is how good the IDE integration is. Thankfully VecTrace has created a good Eclipse plugin for Mercurial. It’s designed to use an external Mercurial executable. So you’ll have to install something like TortoiseHg to do the actually Mercurial work. TortoiseHg is great and on the rare occasion where you can’t get the Eclipse plugin to do what you need, you can always use it, or the command line.

If you are familiar with either the CVS or SVN plugins for Eclipse, the Mercurial one should feel pretty familiar. It’s pretty much the same for the common things like marking a file that needs to be committed, the commit dialog, synchronizing with the main repository, and showing history.

One thing I really like about he Mercurial plugin is the intelligence it uses in marking a file as needing to be committed. With most plugins I’ve used in the past if a file is modified in any way, the IDE flags it has needing to be committed. Even if you undo the changes that you made, it will usually still flag it as needing to be committed. With the Mercurial plugin a file will only be flagged as needing a commit if it’s actually different from the latest version in the repo. So if you change a file, save it, then change it back, it will not show as needing a commit. It’s a small feature, but one I appreciate.

A lot of the time when you have to merge two change sets, the Mercurial will be able to merge them automatically. When there are conflicting changes, however, you’ll have to use the plugin’s merge manager. For the file comparisons it uses the same windows as the other plugins, but there is another view to show the merge status:

In this view you can double click the file with merge conflicts to resolve them. Then you can click ‘Mark resolved’ to mark the file resolved. You can also abort the merge from this view, or mark a file as no resolved.

The last nice view that the plugin has is the History view. Here is picture of the history from my Easyb jUnit project:

The history here shows each change set, who committed it, when it was committed along with the comment for the change set. From this view you can choose to update your code to any change set in the list.

One the left side of the view is the Graph column. This shows how each change set relates to the others. The graph for this project isn’t very interesting since I’m the only developer on this one. So, here’s one from a project with multiple developers:

This graph shows the branching and merging that went on in each change set.

One more nice thing with Mercurial that’s not related to the Eclipse plugin is bitbucket.org. This is the Mercurial equivalent of GitHub. We are currently using it for hosting our repository, and we’re pretty happy with it. It has a lot of nice features, good pricing plans, and allows you to see everything about the project through the web site. There’s also some nice integration with Hudson (which also has a Mercurial plugin) that allows the change descriptions for a Hudson build to link directly to the Bitbucket diff page. Which makes it really easy to se what changed in a particular build and who change it. Good stuff!

To sum it up, I’m really happy with Mercurial. It’s got speed, ease of use, good IDE integration, and a good repository hosting site. I highly recommend it!