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: eposReallyBigProject, and a subfolder is C: eposReallyBigProjectsmall-project. At the command prompt, run:

cd
eposReallyBigProject
split.cmd small-project

This will create C: epossmall-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 .hghgrc file (c: eposReallyBigProject.hghgrc in my example):

[extensions]
hgext.convert=

@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.

To my knowledge, that s not possible. But compared to Subversrion, cloning the whole repos may not be slower than just a branch from SVN.

Quoting from UnderstandingMercurial:

Many SVN/CVS users expect to host related projects together in one repository. This is really not what hg was made for, so you should try a different way of working. This especially means, that you cannot check out only one directory of a repository.

If you absolutely need to host multiple projects in a kind of meta-repository though, you could try the Subrepositories feature that was introduced with Mercurial 1.3 or the older ForestExtension.

@Nick said:

"This is a pretty big omission since a lot hosting sites only offer one repo. With svn I can effectively have as many repos as I want by only taking one branch from the main one. The subrepos sound like a hack."

Subrepos (aka submodules) are not as ideal as "narrow clones" its true. But at least for having many distinct projects in one hosting site s repository, you can have multiple code-bases in one repository. This won t allow you to slice up different sections of one repository / sub-directories of a project , but it will let you manage multiple projects. What you do is have lots of named branches each rooted at the empty (or null) changeset (i.e. they have no common root revision). It can get a little messy to track the branches but it does work.

For example:

hg init
hg branch project-1
# Changes, commits, repeated as needed
hg update null
hg branch project-2
# Changes, commits, repeated as needed

You now can see all your projects:

> hg branches
project-2                      5:42c2beffe780
project-1                      2:43fd60024328

The projects are unrelated (though you can merge them):

> hg debugancestors
-1:000000000000 

Most usefully: you can clone only the project you want, and the others won t mix in:

> hg clone <repository> -r project-1

The graph for this would look something like this (hg log -qG):

@  5 | project-2 | {tip}
|
o  4 | project-2
|
o  3 | project-2

o  2 | project-1
|
o  1 | project-1
|
o  0 | project-1

You can do this for as many projects as you need, listing each with hg branches, and jumping between them with hg update. This takes some care, because named branch support isn t perfect. It isn t always intuitive for one thing (read about hg clone -u in Mercurial 1.4 -- the pre-1.4 behavior is surprising when cloning). But it does work.

Mercurial and Git only permit cloning on the entire repository. Thus it is recommended that each project gets its own repository.

Mercurial has a forest extension to ease having a "forest" for project repositories. The extension keeps each project in a separate repository, but provides options to update/push/pull all the forest repositories together.

It s possible to ask Mercurial to clone just a branch using hg clone -r branchname (see Mercurial clone from a branch).

With Google s NarrowHG extension extension it s possible to perform a narrow clone (see How do I clone a sub-folder of a repository in Mercurial? for a similar question).

I know that it is nearly 10 years after this question was asked, I I stumbled across this question by accident.

There is a new mercurial extension call sparse that allows you to do this.

Here s a possible improvement to Vadim Kotov s solution that supports spaces in the small-project name/subfolder:

@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