Switching branches of freebsd-base-graphics with git

[Thomas Mueller]

I tried to switch freebsd-base-graphics tree from drm-3.8 (something like that, now outdated to drm-next and made a mess.

First, from /freebsd-base-graphics, I did
git checkout drm-next
but then git pull didn't work, I got message about not having repository.

"git checkout drm-next"  switched branches but didn't download anything, hence my try with "git pull".

After some struggle, I did 
git clone https://github.com/FreeBSDDesktop/freebsd-base-graphics.git -b drm-next

from /freebsd-base-graphics directory, but that resuted in the tree being downloaded to /freebsd-base-graphics/freebsd-base-graphics

I recovered by renaming (mv) /freebsd-base-graphics to /freebsd-base-graphics-old, then moved /freebsd-base-graphics-old/freebsd-base-graphics to /
and then, with the new stuff separated from the old, 
rm -R /freebsd-base-graphics-old

That seemed to work, inelegantly.

Question is how to switch the branch and download the new branch over the old, like "svn sw", but with git.

I looked through the documentation, even went to git-scm.org, even a PDF book "Jump-Start Git" but still couldn't see what I should have done.

There has to be a simpler way, but I couldn't find it in the documentation of git.

Tom