Hi Damjan,
we don't plan to support git repos for contributions to l10n.
Having one version control system for our localization team (or two with
svn) is barrier enough, expecting folks to negotiate changes between
different version control systems is really hard.
Alternatively, one could think about supporting git for some locales and
hg for others, but that's really challenging for release automation, and
doc and discoverability.
Also, as ehsan notes, the git mirrors are currently just that, you can
consume the repo in git, but not contribute to it.
As of now, I don't see a value in offering git mirrors for l10n
repositories, and there had to be more than sparse demand for it to
start investing in to it, I guess.
Axel