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

Question

I know there are several threads on this already, but no one has fully explained exactly how to perform the initial diff to create the patch file, then how to apply

Answer 1

I needed to create a patch file and send it to someone so they could update their directory to match mine. There are many caveats with diff and patch however, so it ended up taking me hours to figure out something so conceptually simple. Absolute paths seem to be preferred over relative paths, and many of the options seem to have evolved from niche use cases. I finally figured out a solution based on David H's answer, with additional tips from Lakshmanan Ganapathy):

• Back up your directory to directory.orig
• Modify your directory to reach the desired state
• Save diff from directory.orig to directory in file.patch so name matches for recipient

Here are my notes:

# to create patch:
# copy  backup to something like .orig alongside it
cp -r / /.orig
# create/update/delete files/folders in  until desired state is reached
# change working directory to 
cd /
# create patch file alongside 
diff -Naru ../.orig . > ../file.patch
# -N --new-file Treat absent files as empty.
# -a --text Treat all files as text.
# -r --recursive Recursively compare any subdirectories found.
# -u -U NUM --unified[=NUM] Output NUM (default 3) lines of unified context.

# to apply patch:
# change working directory to 
cd /
patch -s -p0 < /file.patch
# -s or --silent or --quiet Work silently, unless an error occurs.
# -pN or --strip=N Strip smallest prefix containing num leading slashes from files.

# to undo patch (note that directories created by patch must be removed manually):
# change working directory to 
cd /
patch -Rs -p0 < /file.patch
# -R or --reverse Assume that patch was created with the old and new files swapped.
# -s or --silent or --quiet Work silently, unless an error occurs.
# -pN or --strip=N Strip smallest prefix containing num leading slashes from files.