The use of "main" as the default branch in some recent SRFIs (at least
234, 235, 237) breaks tools that assume "master" branch. Currently at
least the `srfi clone` command is affected.
Could we use the same branch name as for the other 200+ SRFIs?
IIRC GitHub changed, or is changing, the default name of the default
branch since some identity politics organization complained about it.