Current package still uses old 'user' eclass. Please port to GLEP 81. If you need help, just ask. P.S.: acct-*/git already exists for several git packages, maybe it could be just used?
https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=646a3fcc850dcbf34cf11198f1445d1aaf2b43ae