How to generate diff header with file index?

Question

Here is the header:

Index: dir1/file1.c
===================================================================
--- dir1.orig/file1.c
+++ dir1/file1.c

How to make diff or git generate such header?

Answer 1

I found out how to generate. It's the header generated by quilt utility. Read more here: How To Survive With Many Patches or Introduction to Quilt