Fix git tfs

Some fix on the tfs parts...

FYI:
* I'm one of the git-tfs developper and the one who has added branch support, among other things....
* My english is not perfect, so feel free to correct it ;) 
First of all, thanks for the `tf history` trick! (And for the git-tfs part in the book!!!)

But I think, that's better, to find the parameters to the `cut` command to cut the whole command line in 2.
See https://github.com/pmiossec/git-tfs/blob/d3722592d1c5399963f6ccc3e60fce351d6d174d/doc/commands/clone.md#map-tfs-users-to-git-users