Bugfix: GIT_EXTERNAL_DIFF with more than one changed files

When there is more than one file that are changed, running git diff with
GIT_EXTERNAL_DIFF incorrectly diagnoses an programming error and dies.
The check introduced in 479b0ae (diff: refactor tempfile cleanup handling,
2009-01-22) to detect a temporary file slot that forgot to remove its
temporary file was inconsistent with the way the codepath to remove the
temporary to mark the slot that it is done with it.

This patch fixes this problem and adds a test case for it.

Signed-off-by: Nazri Ramliy <ayiehere@gmail.com>
Acked-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff.c

@@ -184,8 +184,8 @@ static int remove_tempfile_installed;
 static void remove_tempfile(void)
 {
 	int i;
-	for (i = 0; i < ARRAY_SIZE(diff_temp); i++)
-		if (diff_temp[i].name == diff_temp[i].tmp_path) {
+	for (i = 0; i < ARRAY_SIZE(diff_temp); i++) {
+		if (diff_temp[i].name == diff_temp[i].tmp_path)
 			unlink(diff_temp[i].name);
 		diff_temp[i].name = NULL;
 	}

t/t4020-diff-external.sh

@@ -128,4 +128,12 @@ test_expect_success 'force diff with "diff"' '
 	test_cmp "$TEST_DIRECTORY"/t4020/diff.NUL actual
 '
 
+test_expect_success 'GIT_EXTERNAL_DIFF with more than one changed files' '
+	echo anotherfile > file2 &&
+	git add file2 &&
+	git commit -m "added 2nd file" &&
+	echo modified >file2 &&
+	GIT_EXTERNAL_DIFF=echo git diff
+'
+
 test_done