Recently I realized the fact that not all functionality available for TFVC is supported for Git-mode projects in TFS 2013. This has been indirectly proved by the blog post o
The TFS documentation has a part about details on the differences between TFVC and Git. There is a lot of details, but gated-checkins, "My Work", code review and Source control explorer are the only major features that are not yet supported (and relevant with Git).
There are 2 others features in the file editor which were missing before Visual Studio Update 3 : CodeLens inline history and history annotation.
Code Review option seems to show up in Update 4 with pull requests feature.
Because branches are cheap in Git I can imagine Code Reviews and Gated Check-in will make use of that. Redirect a push to a temporary server side branch and fast-forward merge when the build succeeds, or something like that.
Update: Brian Harry mentions a little bit about in an IMA session he did on reddit: http://www.reddit.com/r/IAmA/comments/17paji/iam_brian_harry_microsoft_technical_fellow_in/c87na4j