How to create and apply a patch in Git

To create a patch, run `git diff > fix.patch` for uncommitted changes, or `git format-patch -1 HEAD` for your last commit. To apply one, run `git apply fix.patch` or `git am 0001-my-change.patch`. Use git apply when you only want the changes in your working folder. Use git am when you want the original commit, with its message and author.

What is a Git patch?

A patch is a text file listing which lines to remove and add in which files. It suits times when you cannot push to the same remote: sending a fix by e-mail, moving a change between unrelated repositories, or keeping a local change outside version control. When you and the other person share a remote, a branch is simpler.

How do I create a patch from uncommitted changes?

# unstaged changes
git diff > fix.patch

# staged changes
git diff --staged > fix.patch

# everything since the last commit
git diff HEAD > fix.patch

# include binary files
git diff --binary > fix.patch

New files that are not staged do not appear in git diff. Run git add on them first and use --staged.

How do I create a patch from commits?

# the last commit
git format-patch -1 HEAD

# the last three commits, one file each
git format-patch -3

# everything on this branch that main does not have
git format-patch main..feature/search -o patches/

# all of it in a single file
git format-patch main --stdout > feature.patch

format-patch writes files named like 0001-add-search-box.patch. Each keeps the commit’s message, author and date, which a plain git diff loses.

How do I apply a patch?

Check it first. These two commands change nothing:

# what it touches
git apply --stat fix.patch

# whether it will apply
git apply --check fix.patch

Then apply it the way you need:

# into the working folder, nothing staged
git apply fix.patch

# into the working folder and the staging area
git apply --index fix.patch

# as commits, with their messages and authors
git am patches/*.patch

What is the difference between git apply and git am?

How do I fix “patch does not apply”?

error: patch failed: src/search.ts:14
error: src/search.ts: patch does not apply

The file changed since the patch was made, so its context lines no longer match. Try these in order:

1. git apply --3way fix.patch uses the original blobs to merge, and leaves normal conflict markers. It needs those blobs in your repository.
2. git apply --whitespace=fix fix.patch helps when only spaces or line endings differ.
3. git apply --reject fix.patch applies what it can and writes the failed parts to .rej files for you to do by hand.
4. Check out the commit the patch was made from, apply it there, then rebase.

For git am, use git am --3way, resolve the conflict, git add the file and run git am --continue. To back out, run git am --abort, as listed in how to abort a merge or rebase.

How do I undo a patch?

git apply -R fix.patch

-R applies the patch in reverse. If you used git am, the commits are normal commits, so undo them with `git reset` or `git revert`.

The guide to creating and applying patches lists every option.