read-tree: add tests for confusing paths like ".." and ".git"

We should prevent nonsense paths from entering the index in
the first place, as they can cause confusing results if they
are ever checked out into the working tree. We already do
so, but we never tested it.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t1014-read-tree-confusing.sh

@@ -0,0 +1,32 @@
+#!/bin/sh
+
+test_description='check that read-tree rejects confusing paths'
+. ./test-lib.sh
+
+test_expect_success 'create base tree' '
+	echo content >file &&
+	git add file &&
+	git commit -m base &&
+	blob=$(git rev-parse HEAD:file) &&
+	tree=$(git rev-parse HEAD^{tree})
+'
+
+while read path; do
+	test_expect_success "reject $path at end of path" '
+		printf "100644 blob %s\t%s" "$blob" "$path" >tree &&
+		bogus=$(git mktree <tree) &&
+		test_must_fail git read-tree $bogus
+	'
+
+	test_expect_success "reject $path as subtree" '
+		printf "040000 tree %s\t%s" "$tree" "$path" >tree &&
+		bogus=$(git mktree <tree) &&
+		test_must_fail git read-tree $bogus
+	'
+done <<-\EOF
+.
+..
+.git
+EOF
+
+test_done