#!/bin/bash
#
# Copyright, the authors of the Linux man-pages project
# SPDX-License-Identifier: GPL-3.0-or-later

set -Eefuo pipefail;
shopt -s lastpipe;

# Defaults:
s='';
u='-u';
w='';

while getopts "sU:w" opt; do
	case "$opt" in
	s)	s='-s';		;;
	U)	u="-U$OPTARG";	;;
	w)	w='-w';		;;
	\?)	exit 1;		;;
	*)	exit 1;		;;
	esac;
done;
shift $((OPTIND-1));

if test $# -gt 2; then
	>&2 echo "$(basename "$0"): error: Too many arguments.";
	exit 1;
fi;

git rev-parse --show-toplevel | read -r dir;
cd "$dir";

test -v MAN_KEEP_FORMATTING || export MAN_KEEP_FORMATTING=1;
test -v MANROFFOPT          || export MANROFFOPT='-d AD=l';

# shellcheck disable=SC2206  # We want only non-empty variables in the array.
opts=($s $w $u);

case $# in
0)  git diff --name-only;		;;
1)  git diff --name-only "$1^..$1";	;;
*)  git diff --name-only "$1..$2";	;;
esac \
| grep -E '(\.[[:digit:]]([[:alpha:]][[:alnum:]]*)?\>|\.man)+(\.man|\.in)*$' \
| sortman \
| while read -r f; do \
	case $# in
	0)  old="HEAD:$f";  new="./$f";   ;;
	1)  old="$1^:$f";   new="$1:$f";  ;;
	*)  old="$1:$f";    new="$2:$f";  ;;
	esac;

	case $# in
	0)  cat "$new";       ;;
	*)  git show "$new";  ;;
	esac \
	| man /dev/stdin \
	| diff -F'^[^ ]' --label "$old" --label "$new" "${opts[@]}" \
		<(git show "$old" | man /dev/stdin) \
		/dev/stdin \
	|| true;
done;