I've found out that sync-c or -c doesnt work so here's an XSLT transform to add clone-depth=1 to all projects in xml
cd .repo/manifests
xsltproc transform.xslt default.xml > default.xml1
rm default.xml
mv default.xml1 default.xml
There's also a shell script that does it for LineageOS.
Comment unneeded repos like darwin and stuff