[root@workstation2017 demo]# git diff old new >cc.diff

[root@workstation2017 demo]# cat cc.diff

diff --git a/old/a/p/foo.txt b/new/a/p/foo.txt

index f041bcd..7351245 100644

--- a/old/a/p/foo.txt

+++ b/new/a/p/foo.txt

@@ -1,2 +1,2 @@

-old_line_1

-old_line_2

+new_line_1

+new_line_2