@@ -0,0 +1,63 @@
+#!/bin/sh
+
+test_description='diff orderfile'
+
+. ./test-lib.sh
+
+test_expect_success 'setup' '
+        as="a a a a a a a a" && # eight a
+        test_write_lines $as >foo &&
+        test_write_lines $as >bar &&
+	git add foo bar &&
+	git commit -a -m initial &&
+        test_write_lines $as b >foo &&
+        test_write_lines $as b >bar &&
+	git commit -a -m first &&
+	test_write_lines bar foo >bar-then-foo &&
+	test_write_lines foo bar >foo-then-bar &&
+	git diff -Ofoo-then-bar HEAD~1..HEAD >diff-foo-then-bar &&
+	git diff -Obar-then-foo HEAD~1..HEAD >diff-bar-then-foo
+'
+
+test_diff_well_formed () {
+	grep ^+b "$1" >added
+	grep ^-b "$1" >removed
+	grep ^+++ "$1" >oldfiles
+	grep ^--- "$1" >newfiles
+	test_line_count = 2 added &&
+	test_line_count = 0 removed &&
+	test_line_count = 2 oldfiles &&
+	test_line_count = 2 newfiles
+}
+
+test_expect_success 'diff output with -O is well-formed' '
+	test_diff_well_formed diff-foo-then-bar &&
+	test_diff_well_formed diff-bar-then-foo
+'
+
+test_expect_success 'flag -O affects diff output' '
+	! test_cmp diff-foo-then-bar diff-bar-then-foo
+'
+
+test_expect_success 'orderfile is same as -O' '
+	test_config diff.orderfile foo-then-bar &&
+	git diff HEAD~1..HEAD >diff-foo-then-bar-config &&
+	test_config diff.orderfile bar-then-foo &&
+	git diff HEAD~1..HEAD >diff-bar-then-foo-config &&
+	test_cmp diff-foo-then-bar diff-foo-then-bar-config &&
+	test_cmp diff-bar-then-foo diff-bar-then-foo-config
+'
+
+test_expect_success '-O overrides orderfile' '
+	test_config diff.orderfile foo-then-bar &&
+	git diff -Obar-then-foo HEAD~1..HEAD >diff-bar-then-foo-flag &&
+	test_cmp diff-bar-then-foo diff-bar-then-foo-flag
+'
+
+test_expect_success '/dev/null is same as no orderfile' '
+	git diff -O/dev/null HEAD~1..HEAD>diff-null-orderfile &&
+	git diff HEAD~1..HEAD >diff-default &&
+	test_cmp diff-null-orderfile diff-default
+'
+
+test_done