dir-iterator: add tests for dir-iterator API

Create t/helper/test-dir-iterator.c, which prints relevant information
about a directory tree iterated over with dir-iterator.

Create t/t0066-dir-iterator.sh, which tests that dir-iterator does
iterate through a whole directory tree as expected.

Signed-off-by: Daniel Ferreira <bnmvco@gmail.com>
[matheus.bernardino: update to use test-tool and some minor aesthetics]
Helped-by: Matheus Tavares <matheus.bernardino@usp.br>
Signed-off-by: Matheus Tavares <matheus.bernardino@usp.br>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t0066-dir-iterator.sh

@@ -0,0 +1,55 @@
+#!/bin/sh
+
+test_description='Test the dir-iterator functionality'
+
+. ./test-lib.sh
+
+test_expect_success 'setup' '
+	mkdir -p dir &&
+	mkdir -p dir/a/b/c/ &&
+	>dir/b &&
+	>dir/c &&
+	mkdir -p dir/d/e/d/ &&
+	>dir/a/b/c/d &&
+	>dir/a/e &&
+	>dir/d/e/d/a &&
+
+	mkdir -p dir2/a/b/c/ &&
+	>dir2/a/b/c/d
+'
+
+test_expect_success 'dir-iterator should iterate through all files' '
+	cat >expected-iteration-sorted-output <<-EOF &&
+	[d] (a) [a] ./dir/a
+	[d] (a/b) [b] ./dir/a/b
+	[d] (a/b/c) [c] ./dir/a/b/c
+	[d] (d) [d] ./dir/d
+	[d] (d/e) [e] ./dir/d/e
+	[d] (d/e/d) [d] ./dir/d/e/d
+	[f] (a/b/c/d) [d] ./dir/a/b/c/d
+	[f] (a/e) [e] ./dir/a/e
+	[f] (b) [b] ./dir/b
+	[f] (c) [c] ./dir/c
+	[f] (d/e/d/a) [a] ./dir/d/e/d/a
+	EOF
+
+	test-tool dir-iterator ./dir >out &&
+	sort out >./actual-iteration-sorted-output &&
+
+	test_cmp expected-iteration-sorted-output actual-iteration-sorted-output
+'
+
+test_expect_success 'dir-iterator should list files in the correct order' '
+	cat >expected-pre-order-output <<-EOF &&
+	[d] (a) [a] ./dir2/a
+	[d] (a/b) [b] ./dir2/a/b
+	[d] (a/b/c) [c] ./dir2/a/b/c
+	[f] (a/b/c/d) [d] ./dir2/a/b/c/d
+	EOF
+
+	test-tool dir-iterator ./dir2 >actual-pre-order-output &&
+
+	test_cmp expected-pre-order-output actual-pre-order-output
+'
+
+test_done