Support finding which commit introduced a regression:
./v run cmd/tools/regress.v --old COMMIT --command './v run /abs/path/to/regression_bug.v'
Support also finding which commit introduced a feature (or made code compile/run):
./v run cmd/tools/regress.v --old COMMIT --command '! ./v run /abs/path/to/feature.v'
NB: the '! ' is a POSIX shell feature. It may not work on Windows outside of WSL.
Its meaning is to invert the exit code for the next command, i.e. 0 -> 1, non 0 -> 0
If it does not work for you, you need to write a more explicit script that will exit
with 0 code for all commits, where the feature does NOT work, and with non 0 code for
all commits, where the feature does work.
