The ebuild dev-vcs/git-1.7.12.3 is based on git-1.7.12-r1 instead of git-1.7.12-r2. That means some useful changes which were introduced with -r2 are now gone. (In particular and unconditial depend on openssl, some OSX fix and the part of the bashcomp script which is responsible for generating a custom shell prompt, git-prompt). Looks like this was an accident.
INCVS.
*** Bug 437946 has been marked as a duplicate of this bug. ***