addftinfo(1) on Linux
The text 4d2c6a3872f4, as Debian 11 (Bullseye) shipped it.
add information to troff font files for use with groff
Flags it lists
-
-asc-height -
-body-depth -
-body-height -
-cap-height -
-comma-depth -
-desc-depth -
-fig-height -
-x-height