diff --stat: report mode-only changes for binary files like text files

Mode-only changes to binary files without content change were reported as
if they were rewritten, but text files in the same situation were reported
as "unchanged". Let's treat binary files like text files here, and simply
say that they are unchanged.

Output of --shortstat is modified in the same way.
Reported-by: NMartin Mareš <mj@ucw.cz>
Signed-off-by: NZbigniew Jędrzejewski-Szmek <zbyszek@in.waw.pl>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

diff.c

@@ -1583,8 +1583,12 @@ static void show_stats(struct diffstat_t *data, struct diff_options *options)
 		if (data->files[i]->is_binary) {
 			fprintf(options->file, "%s", line_prefix);
 			show_name(options->file, prefix, name, len);
-			fprintf(options->file, "  Bin ");
-			fprintf(options->file, "%s%"PRIuMAX"%s",
+			fprintf(options->file, "  Bin");
+			if (!added && !deleted) {
+				putc('\n', options->file);
+				continue;
+			}
+			fprintf(options->file, " %s%"PRIuMAX"%s",
 				del_c, deleted, reset);
 			fprintf(options->file, " -> ");
 			fprintf(options->file, "%s%"PRIuMAX"%s",
@@ -1657,17 +1661,16 @@ static void show_shortstats(struct diffstat_t *data, struct diff_options *option
 		return;
 
 	for (i = 0; i < data->nr; i++) {
-		if (!data->files[i]->is_binary &&
-		    !data->files[i]->is_unmerged) {
-			int added = data->files[i]->added;
-			int deleted= data->files[i]->deleted;
-			if (!data->files[i]->is_renamed &&
-			    (added + deleted == 0)) {
-				total_files--;
-			} else {
-				adds += added;
-				dels += deleted;
-			}
+		int added = data->files[i]->added;
+		int deleted= data->files[i]->deleted;
+
+		if (data->files[i]->is_unmerged)
+			continue;
+		if (!data->files[i]->is_renamed && (added + deleted == 0)) {
+			total_files--;
+		} else {
+			adds += added;
+			dels += deleted;
 		}
 	}
 	if (options->output_prefix) {
@@ -2377,8 +2380,13 @@ static void builtin_diffstat(const char *name_a, const char *name_b,
 
 	if (diff_filespec_is_binary(one) || diff_filespec_is_binary(two)) {
 		data->is_binary = 1;
-		data->added = diff_filespec_size(two);
-		data->deleted = diff_filespec_size(one);
+		if (!hashcmp(one->sha1, two->sha1)) {
+			data->added = 0;
+			data->deleted = 0;
+		} else {
+			data->added = diff_filespec_size(two);
+			data->deleted = diff_filespec_size(one);
+		}
 	}
 
 	else if (complete_rewrite) {

t/t4006-diff-mode.sh

@@ -46,18 +46,12 @@ test_expect_success '--shortstat output after text chmod' '
 
 test_expect_success '--stat output after binary chmod' '
 	test_chmod +x binbin &&
-	cat >expect <<-EOF &&
-	 binbin |  Bin 1024 -> 1024 bytes
-	 1 file changed, 0 insertions(+), 0 deletions(-)
-	EOF
+	echo " 0 files changed" >expect &&
 	git diff HEAD --stat >actual &&
 	test_cmp expect actual
 '
 
 test_expect_success '--shortstat output after binary chmod' '
-	cat >expect <<-EOF &&
-	 1 file changed, 0 insertions(+), 0 deletions(-)
-	EOF
 	git diff HEAD --shortstat >actual &&
 	test_cmp expect actual
 '