A repository does not always have all annexed file contents available.
When you need the content of a file, you can use "git annex get" to
make it available.

We can use this to copy everything in the laptop's annex to the
USB drive.

	# cd /media/usb/annex
	# git fetch laptop; git merge laptop/master
	# git annex get .
	get my_cool_big_file (from laptop...) ok
	get iso/debian.iso (from laptop...) ok
