I can't find the document about the options of hgsubversion.

I don’t know if hg is a possible choice for llvm-project.
Because we can using hgsubversion interactive with subversion.
That’s means we need only an svn server. and create an hg minor.
And we can push to and pull from the subversion server.

I'm not sure about hg, but you can find a git mirror at
earl (Andreas Bolka) · GitHub. You can then use hg-git if you still want to
use hg.