t4051: add test for comments preceding function lines

When showing function context it would be helpful to show comments
immediately before declarations, as they are most likely relevant.

Add a test for that, but without specifying the choice of lines too
rigidly in the test---we may want to stop before and not include
"/*" in the future, for example.

Signed-off-by: Rene Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t4051-diff-function-context.sh

@@ -85,6 +85,10 @@ test_expect_success 'setup' '
 
 check_diff changed_hello 'changed function'
 
+test_expect_failure ' context includes comment' '
+	grep "^ .*Hello comment" changed_hello.diff
+'
+
 test_expect_success ' context includes begin' '
 	grep "^ .*Begin of hello" changed_hello.diff
 '

t/t4051/hello.c

@@ -1,4 +1,7 @@
 
+/*
+ * Hello comment.
+ */
 static void hello(void)	// Begin of hello
 {
 	/*