Can I clone part of a Mercurial repository?

@Nick

"E.g. in Subversion, you might have trunk and branches. If I only want to get trunk (or one of the branches) I can just request [project]/trunk. If I clone the hg repo I'll get trunk and all of the branches. This might be a lot of information I don't want. Can I avoid getting this?"

Absolutely. Just use hg clone -r <branch> and get only the branch you want. If you have lots of branches, you need a -r <branch> for each one. <branch> doesn't have to be a named branch: you can simply have multiple unnamed heads (or named heads using bookmark, though those still aren't perfect, because currently they don't show up with push/pull/clone).

Keep in mind that in DVCSes, Mercurial among them, branches are often short-lived and merged back into each other frequently. If you pull a branch you will still get the common history it has with any other branches.

Yes you can. I'm sure you've moved on, but for the sake of those who will wander here later, I followed the docs at ConvertExtension, and wrote a simple batch script:

@echo off
echo Converting %1
REM Create the file map
echo include %1 > ~myfilemap               
echo rename %1 . >> ~myfilemap 
REM Run the convert process
hg convert --filemap ~myfilemap .\ ..\%1   
REM Delete the file map
del ~myfilemap                             
cd ..\%1
REM update the new repo--to create the files
hg update                                  

Name it something like split.cmd, and put it in the directory for the repo you want to split. Say for example you have C:\repos\ReallyBigProject, and a subfolder is C:\repos\ReallyBigProject\small-project. At the command prompt, run:

cd\repos\ReallyBigProject
split.cmd small-project

This will create C:\repos\small-project with a slice of the relevant history of revisions from the larger project.

The convert is not enabled by default. You'll need to make sure the following lines exist in your .hg\hgrc file (c:\repos\ReallyBigProject\.hg\hgrc in my example):

[extensions]
hgext.convert=