Question

When creating a multi-file unified diff is Index line required like in the following example?

Index: /file1
--- /file1
+++ /file1
_changes in file 1_
Index: /file2
--- /file2
+++ /file2
_changes in file 2_

And what is the purpose of this Index line?

Answer 1

The program patch man page tells that:

If there is an Index: line in the leading garbage and if either the old and new names are both absent or if patch is conforming to POSIX , patch takes the name in the Index: line.

I believe it’s more a “old” thing used for the legacy patch format, and the patch generator that you use still generates that (in contextual and unified format the +++/---/*** lines already do that job). It does not harm.