hgsubversion is an extension for Mercurial that allows using Mercurial as a Subversion client.
Right now it is not ready for production use. You should only be using this if you're ready to hack on it, and go diving into the internals of Mercurial and/or Subversion.
You need to have Subversion installed with the SWIG Python bindings from Subversion 1.5 or later. You need Mercurial 1.3 (currently in development) or later.
If you are unfamiliar with installing Mercurial extensions, please see the UsingExtensions page in the Mercurial wiki. Look at the example for specifying an absolute path near the bottom of the page. You want to give the path to the top level of your clone of this repository.
Before using hgsubversion, I strongly encourage you to run the automated tests. Just use nose if you have it (or easy_install nose if you want it), or use python tests/run.py to run the suite with the conventional test runner. Note that because I use nose, there's a lot of stdout spew in the tests right now. The important part is that all the tests pass.
Get a new clone of an svn server:
$ hg clone <svn URI> [destination]
$ hg clone http://python-nose.googlecode.com/svn nose-hg
Note, you should pull from the root subversion directory, not specific folders (such as trunk).
Pull new revisions into an already-converted repo:
$ hg pull
For more information, see hg help svn while in a converted repo.
Support for svn:externals
All svn:externals properties are serialized into a single .hgsvnexternals file, with the following syntax:
[.] external_reference_line1_1 external_reference_line1_2 [dir2] external_reference_line2_1 external_reference_line2_2
A header line gives the directory the property applies on, '.' for the project root directory. The property content follows, every line being prefixed by a single space.
The creation or modification of this file will trigger svn:externals updates on the related subversion repository.