Why, this is the most confusing error message ever

You get this error

    error: bad index file sha1 signature 
    fatal: index file corrupt 
    fatal: git status --porcelain failed 

and you go to this forum to track it down

http://git.661346.n2.nabble.com/BUG-Confusing-submodule-error-message-td7068110.html

it will say to you simply: you've got a .git directory somewhere in you new .git directory tree. So do 

find . | grep .git

and kill the offending directory or -ries. Now go on.