D-Programming-Language/deimos — comment on commit 65acb7bc0ad63649485b207ede9a59f6fcc95b61
File:  line 0
By braddr:

It's atypical, but it's actually possible for branches to be disconnected from each other, ie, NOT whole repository contents. Take a look at the help for the checkout command, specifically "git checkout --orphan".

I've never used it myself, but it ought to suit this use-case pretty well.