How to create a patch for a whole directory to update it?

I just had this same problem – lots of advice on how to half do it. Well, here is what I did to get both the patching and unpatching to work:

To Create the Patch File:

1. Put copies of both directories in say /tmp, so we can create the patch
   file, or if brave, get them side by side – in one directory.

2. Run an appropriate diff on the two directories, old and new:

   diff -ruN orig/ new/ > file.patch
   # -r == recursive, so do subdirectories
   # -u == unified style, if your system lacks it or if recipient
   #       may not have it, use "-c"
   # -N == treat absent files as empty
   

If a person has the orig/ directory, they can recreate the new one by running patch.

To Recreate the new folder from old folder and patch file:

1. Move the patch file to a directory where the orig/ folder exists

2. This folder will get clobbered, so keep a backup of it somewhere, or
   use a copy.

   patch -s -p0 < file.patch
   # -s == silent except errors
   # -p0 == needed to find the proper folder
   

3. At this point, the orig/ folder contains the new/ content, but still
   has its old name, so:

   mv orig/ new/    # if the folder names are different