./pants help-advanced fetchers | grep mapping
--fetchers-mapping=<mapping> (default: { 'bitbucket\.org/.*':'ArchiveFetcher','golang\.org/x/.*':'ArchiveFetcher','github\.com/.*':'ArchiveFetcher','gopkg\.in/.*':'GopkgInFetcher' })
    A mapping from a remote import path matching regex to a fetcher type to use