fu

#!/bin/sh
set -e

if test $# -lt 1; then
	echo "usage: $0 [-c comment] file" 1>&2
	exit 1
fi

COMMENTS=""
if test $# -gt 1; then
	while test $# -gt 1; do
		case "$1" in
		-c)
			COMMENTS="$2"
			shift
			shift
			;;
		*)
			echo "$0: unknown option $1" 1>&2
			exit 1
		esac
	done
fi
if test \( ! -r "$1" \) -o \( ! -f "$1" \); then
	echo "$0: $1 not a readable file" 1>&2
	exit 1
fi
if test ! -s "$1"; then
	echo "$0: $1 empty" 1>&2
	exit 1
fi

if test ! -d H; then
	mkdir H || (echo "$0: cannot mkdir H" 1>&2; exit 1)
fi

HF="H/H.$1"

if test ! -s "$HF"; then
	echo "a" >>"$HF"
	cat "$1" >>"$HF"
	cat >>"$HF" <<EOF
.

C 1,{{END}}
`date`
init
EOF
	: + 2 because of the 'a' and '.' commands
	LEN=`wc -l "$1" | awk '{print $1 + 2}'`
	ed - "$HF" <<EOF
/^
C 1,{{END}}$/s/{{END}}/$LEN/
w
q
EOF
else
	OLDLEN=`sed '/^
C /q' "$HF"|wc -l|awk '{print $1}'`
	fr -o tmpold "$1"
	STATUS=0
	{ diff -e tmpold "$1" > tmpnew; STATUS=$?; } || :
	if test $STATUS -eq 0; then
		echo "$0: no differences" 1>&2
		rm -f tmpold tmpnew
		exit 1
	elif test $STATUS -eq 2; then
		rm -f tmpold tmpnew
		exit 1
	fi
	if sed -n '1p' tmpnew|grep '^Binary'; then
		echo "$0: $1 is a binary file" 1>&2
		rm -f tmpold tmpnew
		exit 1
	fi
	rm tmpold
	NEWLEN=`wc -l tmpnew|awk "{print \\$1 + $OLDLEN - 1}"`
	if test -z "$COMMENTS"; then
		echo "comments? (EOF to end) "
		COMMENTS=`cat`
	fi
	ed - "$HF" <<EOF
${OLDLEN}-1r tmpnew
\$a

C $OLDLEN,$NEWLEN
`date`
$COMMENTS
.
w
q
EOF
	rm tmpnew
fi

exit 0