### Please describe the problem.
Some filenames in doc have a colon `(:)` in them and it seems it's not allowed on Windows.

There's no hurry with this since I was able to clone the repo by doing a fork on Github and removing `doc/`.

### What steps will reproduce the problem?

[[!format sh """
D:\tmp> git clone git://git-annex.branchable.com/
Cloning into 'git-annex.branchable.com'...
remote: Counting objects: 72064, done.
remote: Compressing objects: 100% (18759/18759), done.
remote: Total 72064 (delta 52959), reused 72032 (delta 52944)
Receiving objects: 100% (72064/72064), 18.05 MiB | 2.39 MiB/s, done.
Resolving deltas: 100% (52959/52959), done.
fatal: cannot create directory at 'doc/bugs/3.20121112:_build_error_in_assistant': Invalid argument
D:\tmp>
"""]]

> [[wontfix|done]] --[[Joey]]
