miscutils/scmfmt

#!/bin/sh
expand |
sed -n '
/./!d
p
i\

:l
n
p
bl' |
sed -n '
:l
p
n
/./bl
:b
n
/./!bb
i\

bl' |
sed  -e '1s/^/./' -e 's/^ /./' |
par -P=. |
awk '
BEGIN { LIMIT = 72 }
NR == 1 || /^[^\.]/ || length($0) < LIMIT {
	sub(/^\./, NR == 1 ? "" : " ");
	print;
}
/^\./ && length($0) >= LIMIT {
	sub(/^\./, " ");
	print substr($0, 1, LIMIT)"\\";
	for (i = 2*LIMIT - length($0) + 1; i; i--)
		printf " ";
	print substr($0, LIMIT+1);
}'