Note: there happens to be a bug with hg convert if you perform this command from a directory other than the source directory.
You will get the following error:
abort: cannot read tags from git-repo4/.git
Confirmed with git 1.7.9 and Mercurial 2.6.2 on Windows XP
The hg convert utility isn't on by default after installation. In order to set it as such add the following to your .hgrc file.
[extensions]
hgext.convert=
If you're using TortoiseHg on Windows then this file resides in your home directory as mercurial.ini. After this setting change you will be able to use the hg convert utility.
The convert extension may work for you, but if it doesn't, you might want to check out tailor which is a general purpose tool for converting among the various distributed SCMs.
This plugin is originally developped by the guys of GitHub, and allows the convert from git<->mercurial losslessly. In theory, you could even be able to clone the hg repository.