I've been told by knowledgeable people that it is impossible to
implement composable continuations (AKA delimited continuations AKA
shift/reset) in terms of call-with-current-continuation. Since I
don't yet understand why that is, I figured it would help my
understanding to attempt it and see how it fails.
Previously, I used a shell script to extract modification date ranges
from the Git history, but that was complicated and unreliable, so now
every file just gets the same year range in its copyright header. If
someone needs to know when a specific file was modified and by whom,
they can look at the Git history themselves; no need to include it
redundantly in the header.
