+hc=()
+cc=()
+cformat='%(trailers:only=no,valueonly,unfold,key=signed-off-by)%aN <%aE>%n%cN <%cE>'
+
+read -r -a head_commits -p 'HEAD commit(s): '
+for c in "${head_commits[@]}"; do
+ if ! git rev-parse --verify "$c" >/dev/null; then
+ printf 'Unknown commit %s\n' "$c"
+ exit 1
+ fi
+ hc+=( "$(git log -1 --format='%h ("%s")' "$c")" )
+ readarray -t -O "${#cc[@]}" cc < <(git log -1 --format="$cformat" "$c" | sort -u)
+done
+