Recently there have been a few changes to the MercurialEclipse project which is what I have recommended in the past to use to enable Mercurial source control in Domino Designer so if you need to use Mercurial here are the updated instructions that I’ve been able to get working.
The first big change is that the project has moved from JavaForge to BitBucket so the update site has also changed. Its new URL is http://mercurialeclipse.eclipselabs.org.codespot.com/hg.wiki/update_site/stable
When installing the MercurialEclipse plugin you do need to install an older version. I’ve found the highest version of the plugin that works is V1.7.2, anything higher and the Mercurial options don’t appear anywhere in Domino Designer. This is due to the fact that Domino Designer is based on Eclipse v3.4 and the newer MercurialEclipse builds require a minimum of Eclipse 3.5
Secondly the update site no longer contains the Mercurial binaries, you will need to install Mercurial manually on your machine yourself. You can download Mercurial from here. I used the standard MSI installer for my testing and found that the latest version ( v2.3.2 ) worked fine. Once installed you need to tell the MercurialEclipse plugin where the binaries are. To do this load up the File -> Preferences menu in Domino Designer and then go to the Team – Mercurial menu and then set that path to hg.exe in the options.
Once the link between Mercurial and MercurialEclipse is set then your all done.
Hope this helps somebody out.
Dec's Dom Blog 