[ubercow13]

It's like shorthand for git checkout <current branch> -- <files>. You're only omitting the current branch which is the default. I'm not sure if it's intuitive but it seems pretty coherent.

edit: on second thought no it's really not very coherent. If you exclude <files> it means checkout all files if you write a <branch>, but no files if you write no <branch>. So excluding <branch> doesn't consistently do the same as using <current branch>. I guess git does kind of suck.