Isso deve fazer isso:
repo sync -c --no-tags --no-clone-bundle -j'nproc'
Explicação das opções:
repo sync -h
-c, --current-branch fetch only current branch from server
--no-tags don't fetch tags
--no-clone-bundle disable use of /clone.bundle on HTTP/HTTPS
-j JOBS, --jobs=JOBS projects to fetch simultaneously (default 4)
...