#!/bin/bash

set -e

NLINES=50000
NRAND=32768
# probability of change in percent
CHG_PROB=30
perf=
while test $# -gt 0
do
	case $1 in
	-p)
		perf=t
		;;
	-n)
		shift
		NLINES=$1
		;;
	*)
		break
		;;
	esac
	shift
done

if test $# -gt 0
then
	export PATH="$1:$PATH"
	shift
fi

if test $# -gt 0
then
	echo "too many arguments" >&2
	exit 1
fi

dir=$(mktemp -d)

scramble()
{
	while read x
	do
		if test $RANDOM -lt $((($CHG_PROB * $NRAND)/100))
		then
			echo $RANDOM
		else
			echo "$x"
		fi
	done < "$1" > "$1.new"
	mv -f "$1.new" "$1"
}

run()
{
	echo \$ "$@"
	if test -n "$perf"
	then
		perf record -g -f "$@" >/dev/null
		perf report -g
	else
		time "$@" >/dev/null
	fi
}

cd "$dir"
git init -q

for i in $(seq $NLINES)
do
	echo $i
done > file
git add file
echo "file binary" >.gitattributes
git add .gitattributes
git commit -q -m initial
git branch other

scramble file
git add file
git commit -q -m 'change big file'

git checkout -q other
: >newfile
git add newfile
git commit -q -m 'add small file'

gfp="git format-patch --stdout"

run $gfp master
run $gfp --ignore-if-in-upstream master

git cherry-pick master >/dev/null 2>&1

git checkout -q master
scramble file
git add file
git commit -q -m 'change big file again'

git checkout -q other^{}
run git rebase master
if test -n "$(git rev-list master...HEAD~)"
then
	echo "patch not identified" >&2
	exit 1
fi

git checkout -q -b squashed master
git reset -q --soft HEAD~2
git commit -q -m squashed
git checkout -q other^{}
if git rebase squashed >/dev/null
then
	echo "patch dropped" >&2
	exit 1
fi

cd - >/dev/null
rm -rf "$dir"