The PostgreSQL developers team lives on the pgsql-hackers mailing list (http://www.postgresql.org/list/pgsql-hackers/) which is appropriate for discussion of current development issues, problems and bugs, and PROPOSED NEW FEATURES. =)
But it's not a postgresql feature, it's a libgit feature. That said, you might still get a review out of it, but it's certainly not the obviously correct place.
See also http://www.postgresql.org/developer/