1. hg-git, both libraries were started by githubbers to get the market of people-who-want-to-use-hg on github
2. interfacing with git repos from python, doing so through subprocess is less than enjoyable (and libgit2 basically didn't exist at the time) (and requires C code, which may be a chore e.g. on windows)
I wanted to speed up hg-git, since it's really slow for moderately-sized git repos. The slowness seems to be all in Dulwich. Isn't it more desirable then to have Python bindings to libgit?
I think there's a bunch of speeding-up hg-git work floating around, notably around Mozilla work. Some of that has been mentioned in the hg-git mailing list.
2. interfacing with git repos from python, doing so through subprocess is less than enjoyable (and libgit2 basically didn't exist at the time) (and requires C code, which may be a chore e.g. on windows)