repository_root sets the global root URL that will be used when downloading files and packages using fetch(3) and friends.
Recognised URLs must begin with "http://" (HTTP), "https://" (HTTPS), "ftp://" (FTP), ":pserver:" (CVS via pserver) or ":ext:" (CVS via SSH).
The global repository root can be overridden by all functions that downloads files and packages by giving the root=url option to those functions.
Check out files and packages from CVS by default:
Download files and packages via HTTP by default: