Now
MAIN commitmail json YAML
Earliest reference to /dev/null I can find is in v4 sh(1) and nulldev in
nsys/ken/subr.c
via TUHS archive
https://minnie.tuhs.org/cgi-bin/utree.pl?file=V4
nsys/ken/subr.c
via TUHS archive
https://minnie.tuhs.org/cgi-bin/utree.pl?file=V4