diff --git a/Documentation/diff-config.txt b/Documentation/diff-config.txt
index 223b931..f07b451 100644
--- a/Documentation/diff-config.txt
+++ b/Documentation/diff-config.txt
@@ -98,6 +98,11 @@
 diff.noprefix::
 	If set, 'git diff' does not show any source or destination prefix.
 
+diff.orderfile::
+	File indicating how to order files within a diff, using
+	one shell glob pattern per line.
+	Can be overridden by the '-O' option to linkgit:git-diff[1].
+
 diff.renameLimit::
 	The number of files to consider when performing the copy/rename
 	detection; equivalent to the 'git diff' option '-l'.
diff --git a/Documentation/diff-options.txt b/Documentation/diff-options.txt
index bbed2cd..9b37b2a 100644
--- a/Documentation/diff-options.txt
+++ b/Documentation/diff-options.txt
@@ -432,6 +432,9 @@
 -O<orderfile>::
 	Output the patch in the order specified in the
 	<orderfile>, which has one shell glob pattern per line.
+	This overrides the `diff.orderfile` configuration variable
+	(see linkgit:git-config[1]).  To cancel `diff.orderfile`,
+	use `-O/dev/null`.
 
 ifndef::git-format-patch[]
 -R::
diff --git a/diff.c b/diff.c
index f99bc83..6b4cd0e 100644
--- a/diff.c
+++ b/diff.c
@@ -30,6 +30,7 @@
 static int diff_context_default = 3;
 static const char *diff_word_regex_cfg;
 static const char *external_diff_cmd_cfg;
+static const char *diff_order_file_cfg;
 int diff_auto_refresh_index = 1;
 static int diff_mnemonic_prefix;
 static int diff_no_prefix;
@@ -201,6 +202,8 @@
 		return git_config_string(&external_diff_cmd_cfg, var, value);
 	if (!strcmp(var, "diff.wordregex"))
 		return git_config_string(&diff_word_regex_cfg, var, value);
+	if (!strcmp(var, "diff.orderfile"))
+		return git_config_pathname(&diff_order_file_cfg, var, value);
 
 	if (!strcmp(var, "diff.ignoresubmodules"))
 		handle_ignore_submodules_arg(&default_diff_options, value);
@@ -3219,6 +3222,8 @@
 	options->detect_rename = diff_detect_rename_default;
 	options->xdl_opts |= diff_algorithm;
 
+	options->orderfile = diff_order_file_cfg;
+
 	if (diff_no_prefix) {
 		options->a_prefix = options->b_prefix = "";
 	} else if (!diff_mnemonic_prefix) {
diff --git a/diffcore-order.c b/diffcore-order.c
index 50c089b..fe7f1f4 100644
--- a/diffcore-order.c
+++ b/diffcore-order.c
@@ -10,28 +10,21 @@
 
 static void prepare_order(const char *orderfile)
 {
-	int fd, cnt, pass;
+	int cnt, pass;
+	struct strbuf sb = STRBUF_INIT;
 	void *map;
 	char *cp, *endp;
-	struct stat st;
-	size_t sz;
+	ssize_t sz;
 
 	if (order)
 		return;
 
-	fd = open(orderfile, O_RDONLY);
-	if (fd < 0)
-		return;
-	if (fstat(fd, &st)) {
-		close(fd);
-		return;
-	}
-	sz = xsize_t(st.st_size);
-	map = mmap(NULL, sz, PROT_READ|PROT_WRITE, MAP_PRIVATE, fd, 0);
-	close(fd);
-	if (map == MAP_FAILED)
-		return;
+	sz = strbuf_read_file(&sb, orderfile, 0);
+	if (sz < 0)
+		die_errno(_("failed to read orderfile '%s'"), orderfile);
+	map = strbuf_detach(&sb, NULL);
 	endp = (char *) map + sz;
+
 	for (pass = 0; pass < 2; pass++) {
 		cnt = 0;
 		cp = map;
diff --git a/t/t4056-diff-order.sh b/t/t4056-diff-order.sh
new file mode 100755
index 0000000..1ddd226
--- /dev/null
+++ b/t/t4056-diff-order.sh
@@ -0,0 +1,104 @@
+#!/bin/sh
+
+test_description='diff order'
+
+. ./test-lib.sh
+
+create_files () {
+	echo "$1" >a.h &&
+	echo "$1" >b.c &&
+	echo "$1" >c/Makefile &&
+	echo "$1" >d.txt &&
+	git add a.h b.c c/Makefile d.txt &&
+	git commit -m"$1"
+}
+
+test_expect_success 'setup' '
+	mkdir c &&
+	create_files 1 &&
+	create_files 2 &&
+
+	cat >order_file_1 <<-\EOF &&
+	*Makefile
+	*.txt
+	*.h
+	EOF
+
+	cat >order_file_2 <<-\EOF &&
+	*Makefile
+	*.h
+	*.c
+	EOF
+
+	cat >expect_none <<-\EOF &&
+	a.h
+	b.c
+	c/Makefile
+	d.txt
+	EOF
+
+	cat >expect_1 <<-\EOF &&
+	c/Makefile
+	d.txt
+	a.h
+	b.c
+	EOF
+
+	cat >expect_2 <<-\EOF
+	c/Makefile
+	a.h
+	b.c
+	d.txt
+	EOF
+'
+
+test_expect_success "no order (=tree object order)" '
+	git diff --name-only HEAD^..HEAD >actual &&
+	test_cmp expect_none actual
+'
+
+test_expect_success 'missing orderfile' '
+	rm -f bogus_file &&
+	test_must_fail git diff -Obogus_file --name-only HEAD^..HEAD
+'
+
+test_expect_success POSIXPERM,SANITY 'unreadable orderfile' '
+	>unreadable_file &&
+	chmod -r unreadable_file &&
+	test_must_fail git diff -Ounreadable_file --name-only HEAD^..HEAD
+'
+
+test_expect_success 'orderfile is a directory' '
+	test_must_fail git diff -O/ --name-only HEAD^..HEAD
+'
+
+for i in 1 2
+do
+	test_expect_success "orderfile using option ($i)" '
+		git diff -Oorder_file_$i --name-only HEAD^..HEAD >actual &&
+		test_cmp expect_$i actual
+	'
+
+	test_expect_success PIPE "orderfile is fifo ($i)" '
+		rm -f order_fifo &&
+		mkfifo order_fifo &&
+		{
+			cat order_file_$i >order_fifo &
+		} &&
+		git diff -O order_fifo --name-only HEAD^..HEAD >actual &&
+		wait &&
+		test_cmp expect_$i actual
+	'
+
+	test_expect_success "orderfile using config ($i)" '
+		git -c diff.orderfile=order_file_$i diff --name-only HEAD^..HEAD >actual &&
+		test_cmp expect_$i actual
+	'
+
+	test_expect_success "cancelling configured orderfile ($i)" '
+		git -c diff.orderfile=order_file_$i diff -O/dev/null --name-only HEAD^..HEAD >actual &&
+		test_cmp expect_none actual
+	'
+done
+
+test_done