[PATCH v2] diff: Add diff.orderfile configuration variable

@@ -98,6 +98,11 @@ diff.mnemonicprefix::
 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'.

@@ -432,6 +432,8 @@ endif::git-format-patch[]
 -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]).
 
 ifndef::git-format-patch[]
 -R::

@@ -30,6 +30,7 @@ static int diff_use_color_default = -1;
 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 @@ int git_diff_ui_config(const char *var, const char *value, void *cb)
 		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_string(&diff_order_file_cfg, var, value);
 
 	if (!strcmp(var, "diff.ignoresubmodules"))
 		handle_ignore_submodules_arg(&default_diff_options, value);

@@ -3207,6 +3210,8 @@ void diff_setup(struct diff_options *options)
 	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) {

@@ -0,0 +1,79 @@
+#!/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"
+	return $?
+}
+
+test_expect_success "setup" '
+	mkdir c &&
+	create_files 1 &&
+	create_files 2
+'
+
+cat >order_file_1 <<EOF
+*Makefile
+*.txt
+*.h
+*
+EOF
+cat >order_file_2 <<EOF
+*Makefile
+*.h
+*.c
+*
+EOF
+
+cat >expect_diff_headers_none <<EOF
+diff --git a/a.h b/a.h
+diff --git a/b.c b/b.c
+diff --git a/c/Makefile b/c/Makefile
+diff --git a/d.txt b/d.txt
+EOF
+
+cat >expect_diff_headers_1 <<EOF
+diff --git a/c/Makefile b/c/Makefile
+diff --git a/d.txt b/d.txt
+diff --git a/a.h b/a.h
+diff --git a/b.c b/b.c
+EOF
+
+cat >expect_diff_headers_2 <<EOF
+diff --git a/c/Makefile b/c/Makefile
+diff --git a/a.h b/a.h
+diff --git a/b.c b/b.c
+diff --git a/d.txt b/d.txt
+EOF
+
+test_expect_success "no order (=tree object order)" '
+	git diff HEAD^..HEAD >patch &&
+	grep ^diff patch >actual_diff_headers &&
+	test_cmp expect_diff_headers_none actual_diff_headers
+'
+
+for i in 1 2; do
+	test_expect_success "orderfile using option ($i)" "
+	git diff -Oorder_file_$i HEAD^..HEAD >patch &&
+	grep ^diff patch >actual_diff_headers &&
+	test_cmp expect_diff_headers_$i actual_diff_headers
+"
+done
+
+for i in 1 2; do
+	test_expect_success "orderfile using config ($i)" "
+	git -c diff.orderfile=order_file_$i diff HEAD^..HEAD >patch &&
+	grep ^diff patch >actual_diff_headers &&
+	test_cmp expect_diff_headers_$i actual_diff_headers
+"
+done
+
+test_done