git: How do I recursively add all files in a directory subtree that match a glob pattern?

It’s a bug in the documentation. Quote the asterisk with

$ git add documentation/\*.screen

or

$ git add 'documentation/*.screen'

to get the behavior you want.

If instead you want to add files in the current directory only, use

$ git add *.screen

UPDATE: I submitted a patch that corrects the issue, now fixed as of version 1.6.6.2.