I created a quick batch file, but you need to have Team Foundation Power Tools (tfpt.exe) in your path and For (a command line loop command)
Visual Studio Command line to your desired git folder and run the following.
git log --pretty="'%H',%ci - %s" --reverse > commits
tf workspace temp /new /s:http://{TfsInstance} /i
tf workfold /map %2 . /workspace:temp
FOR /F "tokens=1* delims=','" %%a IN (commits) DO git checkout %%a && tfpt online /recursive /exclude:.git*,commits,*.obj,*.exe,_ReSharper*,obj,debug,*.user,*.suo,Bin /adds /deletes /i && tf checkin /author:"{AuthorName}" /comment:"%%b" /i
tf workspace temp /delete /i
First it creates a commits file with all the commit information in reverse order (earliest first).
Then it creates a Team Foundation workspace... (be sure to replace {TtsInstance} with your TFS uri.
Then it creates a temporary folder in the workspace.
Thne it loops through each line in the commits file, does a checkout from git, uses TFPT to check in the current files (again be sure to replace {AuthorName} with your author name) the comment will include the timestamp from git (unfortunetly you can't change checkin time without changing the TFS server's time and I would recommend against that) and the original author's name.
This worked okay, but branches won't be perserved. I didn't take the time to figure out branching since it wasn't a big enough factor for the job at the time.
Hopefully this can save someone some time!