t1010: add mktree test

So far mktree (which has always been a quick hack) had no test.
At least give it a bit of test coverage.
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

t/t1010-mktree.sh

+#!/bin/sh
+
+test_description='git mktree'
+
+. ./test-lib.sh
+
+test_expect_success setup '
+	for d in a a. a0
+	do
+		mkdir "$d" && echo "$d/one" >"$d/one" &&
+		git add "$d"
+	done &&
+	echo one >one &&
+	git add one &&
+	git write-tree >tree &&
+	git ls-tree $(cat tree) >top &&
+	git ls-tree -r $(cat tree) >all &&
+	test_tick &&
+	git commit -q -m one &&
+	H=$(git rev-parse HEAD) &&
+	git update-index --add --cacheinfo 160000 $H sub &&
+	test_tick &&
+	git commit -q -m two &&
+	git rev-parse HEAD^{tree} >tree.withsub &&
+	git ls-tree HEAD >top.withsub &&
+	git ls-tree -r HEAD >all.withsub
+'
+
+test_expect_success 'ls-tree piped to mktree (1)' '
+	git mktree <top >actual &&
+	test_cmp tree actual
+'
+
+test_expect_success 'ls-tree piped to mktree (2)' '
+	git mktree <top.withsub >actual &&
+	test_cmp tree.withsub actual
+'
+
+test_expect_success 'ls-tree output in wrong order given to mktree (1)' '
+	perl -e "print reverse <>" <top |
+	git mktree >actual &&
+	test_cmp tree actual
+'
+
+test_expect_success 'ls-tree output in wrong order given to mktree (2)' '
+	perl -e "print reverse <>" <top.withsub |
+	git mktree >actual &&
+	test_cmp tree.withsub actual
+'
+
+test_expect_failure 'mktree reads ls-tree -r output (1)' '
+	git mktree <all >actual &&
+	test_cmp tree actual
+'
+
+test_expect_failure 'mktree reads ls-tree -r output (2)' '
+	git mktree <all.withsub >actual &&
+	test_cmp tree.withsub actual
+'
+
+test_done