Strange checkout message

[Simon Peyton Jones]

Herbert or others,
What does this mean (in a clean tree)

git checkout wip/orf

Checking out files: 100% (159/159), done.

M    utils/haddock

Branch wip/orf set up to track remote branch wip/orf from origin.

Switched to a new branch 'wip/orf'

simonpj at cam-05-unx:~/code/HEAD-3$
What's all this about haddock being modified?  I've just checked out a branch, which is supposed to make everything line up, isn't it?
Do you need to say "git submodule update" as well?
Could this be documented in the (upcoming?) workflows page?
Thanks
Simon

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