Or does it need to be in one repository?
Yes, SPYN allows you to pull code from multiple GIT repos. Both the Web_UI and CLI client allows for https:// GIT URLS to be specified per module.
SPYN manages source-code in 3 parts.
Source code of the Odoo Core
Odoo standard modules
- Customized modules
Each of these parts can be sourced from a different repository.