Document the purpose of the script

There was no explanation on why the script should be used, 
so I added a comment on that.

Author: rajaravivarma-r

git-amend-all

@@ -6,6 +6,8 @@
 ## This is free software, and you are welcome to redistribute it
 ## under certain conditions; see COPYING for details.
 
+# Purpose: This script adds all modified and deleted files, 
+# except the new files and adds it to the recent commit by amending it
 
 set -e