git and peer review

I have tried many online review tools: cucible, reviewboard and smartcollaborator. The are both great. However, they can't satisfy all my requirements:

1. poor git support
2. When reviewing changes between revision (or commit for git) a and
revision b, they display all changes as a single diff instead of one
diff for each intermediate revision

So finally, i decide to use git itself as the reviewing tool if i can't find better.

I am in a company environment and i want to enforce a policy that every commit must be reviewed before pushed to central repository. I think i can use hooks to enforce such kind of policy.

One way i want to try is to check in the hook whether every pushed commit has a "Reviewed-by " line . Any suggestion?

And one question, how to add a "Reviewed-by" line automatically?

The reviewers sit near each other, so we do face-to-face peer review and don't pass patches by email. Say, i have prepared a patch series,

Case 1
    I ask someone to review my patches at my machine. If the review
passes, i have to add Reviewed-by line to each commit and then merge
it to the master branch. However, i find no easy way to add
reviewed-by line. Maybe adding --reviewed-by  option to cherry-pick or
rebase or merge?

Case 2
   The reviewer is the maintainer, so i ask him to pull and review. So
now it is his turn to add review-by line. But still, how?