You should be able to edit any imported layer to specify a Git repository for it instead of a directory, or a directory instead of a Git repository.
Created attachment 3284 [details] Design - Edit imported layers
Created attachment 3301 [details] Design - Edit imported layers Some small changes to the layer details page in the text that explains the layer source options, following some feedback from contributors.
This work has been merged http://git.yoctoproject.org/cgit/cgit.cgi/poky/commit/?id=fa48ca677c75d01cebe4e5d6519ed71c588fd93d