diff: rename "set" variable

Once upon a time the builtin_diff function used one color, and the color
variables were called "set" and "reset". Nowadays it is a much longer
function and we use several colors (e.g., "add", "del"). Rename "set" to
"meta" to show that it is the color for showing diff meta-info (it still
does not indicate that it is a "color", but at least it matches the
scheme of the other color variables).

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

diff.c

@@ -2238,7 +2238,7 @@ static void builtin_diff(const char *name_a,
 	mmfile_t mf1, mf2;
 	const char *lbl[2];
 	char *a_one, *b_two;
-	const char *set = diff_get_color_opt(o, DIFF_METAINFO);
+	const char *meta = diff_get_color_opt(o, DIFF_METAINFO);
 	const char *reset = diff_get_color_opt(o, DIFF_RESET);
 	const char *a_prefix, *b_prefix;
 	struct userdiff_driver *textconv_one = NULL;
@@ -2285,24 +2285,24 @@ static void builtin_diff(const char *name_a,
 	b_two = quote_two(b_prefix, name_b + (*name_b == '/'));
 	lbl[0] = DIFF_FILE_VALID(one) ? a_one : "/dev/null";
 	lbl[1] = DIFF_FILE_VALID(two) ? b_two : "/dev/null";
-	strbuf_addf(&header, "%s%sdiff --git %s %s%s\n", line_prefix, set, a_one, b_two, reset);
+	strbuf_addf(&header, "%s%sdiff --git %s %s%s\n", line_prefix, meta, a_one, b_two, reset);
 	if (lbl[0][0] == '/') {
 		/* /dev/null */
-		strbuf_addf(&header, "%s%snew file mode %06o%s\n", line_prefix, set, two->mode, reset);
+		strbuf_addf(&header, "%s%snew file mode %06o%s\n", line_prefix, meta, two->mode, reset);
 		if (xfrm_msg)
 			strbuf_addstr(&header, xfrm_msg);
 		must_show_header = 1;
 	}
 	else if (lbl[1][0] == '/') {
-		strbuf_addf(&header, "%s%sdeleted file mode %06o%s\n", line_prefix, set, one->mode, reset);
+		strbuf_addf(&header, "%s%sdeleted file mode %06o%s\n", line_prefix, meta, one->mode, reset);
 		if (xfrm_msg)
 			strbuf_addstr(&header, xfrm_msg);
 		must_show_header = 1;
 	}
 	else {
 		if (one->mode != two->mode) {
-			strbuf_addf(&header, "%s%sold mode %06o%s\n", line_prefix, set, one->mode, reset);
-			strbuf_addf(&header, "%s%snew mode %06o%s\n", line_prefix, set, two->mode, reset);
+			strbuf_addf(&header, "%s%sold mode %06o%s\n", line_prefix, meta, one->mode, reset);
+			strbuf_addf(&header, "%s%snew mode %06o%s\n", line_prefix, meta, two->mode, reset);
 			must_show_header = 1;
 		}
 		if (xfrm_msg)

t/t4041-diff-submodule-option.sh

@@ -71,6 +71,21 @@ EOF
 	test_cmp expected actual
 "
 
+test_expect_success 'diff.submodule does not affect plumbing' '
+	test_config diff.submodule log &&
+	git diff-index -p HEAD >actual &&
+	cat >expected <<-EOF &&
+	diff --git a/sm1 b/sm1
+	new file mode 160000
+	index 0000000..a2c4dab
+	--- /dev/null
+	+++ b/sm1
+	@@ -0,0 +1 @@
+	+Subproject commit $fullhead1
+	EOF
+	test_cmp expected actual
+'
+
 commit_file sm1 &&
 head2=$(add_file sm1 foo3)