#!/bin/sh
git log --pretty=%b%x00 "$@" |
perl -n0 -wMstrict -E '
	for (reverse split /\n\n/) {
		my @headers = grep m{
			^ (?: [a-z]+ (?: (?:-\w+)+ | \ by ) ) : \s* \S
		}imx, split /\n/ or next;
		say for @headers;
		last;
	}
'