v2.6.11 tag in kernel tree

Using this tree git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6

These two tags appear to be pointing to a tree instead of a commit.
v2.6.11
v2.6.11-tree

I'm trying to check out v2.6.11 so that I can figure out the changes a
vendor made to it.

jonsmirl@jonsmirl:/extra/linux$ git checkout -b microcross v2.6.11
Cannot switch branch to a non-commit.

I can checkout the other tags without problem.

What's the secret to checking out 2.6.11?

-- 
Jon Smirl