How to apply a patch generated with git format-patch?

Question

I have two local git repositories, both pointing to the same remote repository.

In one git repository, if I do git format-patch 1, how can I apply that patch to the other repository?

Fishnet

Related: 1) What is the difference between git am and git apply?, 2) How to configure and use git send-email to work with gmail to email patches to developers – Klinges

Answer 1

Note: You can first preview what your patch will do:

First the stats:

git apply --stat a_file.patch

Then a dry run to detect errors:

git apply --check a_file.patch

Finally, you can use git am to apply your patch as a commit. This also allows you to sign off an applied patch.
This can be useful for later reference.

git am --keep-cr --signoff < a_file.patch 

As noted by riverofwind in the comments:

Don't forget if you have autocrlf=false for Windows only development you'll need to pass --keep-cr to am to keep those CRLFs

See an example in this article:

In your git log, you’ll find that the commit messages contain a “Signed-off-by” tag. This tag will be read by Github and others to provide useful info about how the commit ended up in the code.

Resentful

git am < somepatch.patch yields "fatal: empty ident name (for <>) not allowed". Can someone explain to me why? – Organization

@gromit190 that means bad Author headers in the patch, and/or you didn't git config user.{name,email}. – Radiobiology

OK; git apply --check says patch does not apply, and git apply -3 says repository lacks the necessary blob to fall back on 3-way merge. In git, rebasing commits is such a breeze; but how do people rebase their patches on top of updated code? – Radiobiology

@Radiobiology Maybe with https://mcmap.net/q/12287/-git-apply-fails-with-quot-patch-does-not-apply-quot-error ? – Resentful

@Resentful how can i get back, before to apply the patch? – Pacheco

Also don't forget if you have autocrlf=false for Windows only development you'll need to pass --keep-cr to am to keep those crlfs – Malloch

Answer 2

git apply name-of-file.patch

Waterside

This may not have answered the original detailed question but it answered the question in the title which is why I am on this page. thank you! – Barnebas

I understand this is an old question and answer... but I thought it may be helpful to some people to understand the difference between git apply and git am. – Tireless

git apply "[...full path to the file...]/name-of-file.patch" – Burning

Answer 3

Or, if you're kicking it old school:

cd /path/to/other/repository
patch -p1 < 0001-whatever.patch

Toothpaste

Just so you're aware: That won't create a commit, so it will lose commit message and author information. – Abana

I've had some cases where this works when git apply doesnt, not sure why – Erudition

This is very useful if you are trying to apply a patch to a path or file that is ignored by Git and you have a Git formatted patch. – Knockknee

Indeed, extremely useful when trying to apply a git generated patch on a machine that does not have git installed (docker images for example) – Mantis

Thanks sir! Worked for me when git apply just didn't do anything. – Mercantilism

@Dominic. Can you do that in a single line? Like git commit | patch -p0/1 – Spermatophore

@Spermatophore Sure. Use a pipe. If you need to change directories, etc. in between consider using named pipes. – Toothpaste

Answer 4

First you should take a note about difference between git am and git apply

When you are using git am you usually wanna to apply many patches. Thus should use:

git am *.patch

or just:

git am

Git will find patches automatically and apply them in order ;-)

UPD
Here you can find how to generate such patches

Throw

This explanation of the difference helped me to use git apply .. and in --reverse :-) 👍 – Stonemason

Do you happen to know what “am” is supposed to stand for? Maybe “apply en masse”? ;) – Sewing

@fitojb, am may stand for "apply mail", since patches used to be emailed around a lot. See this comment here: What is the difference between git am and git apply? – Klinges

Answer 5

If you want to apply it as a commit, use git am.

Disproportion

How do you usually get the mbox files in the first place? – Gastrovascular

or just use git apply – Ethical

@Ethical : git apply applies changes as a patch, not as a commit, while git am assumes that the text of the email is the commit message (with some exceptions) and applies changes creating a commit (and it can try to resolve conflicts with 3-way merge with git am --3way. – Vestment

I cannot get git am to work. It stops in the middle applying changes and the commit generated is incomplete – Enrika

@Enrika : there might be a content conflict when applying changes, but there is not enough information in your comment; please post the problem as a question, with as much detail as possible. – Vestment

Answer 6

If you're using a JetBrains IDE (like IntelliJ IDEA, Android Studio, PyCharm), you can drag the patch file and drop it inside the IDE, and a dialog will appear, showing the patch's content. All you have to do now is to click "Apply patch", and a commit will be created.

Afoul

@LasithaBenaragama - kind of. SO is meant to not only help the OP, but also everyone who follows. This answer (while useful) doesn't provide a general solution. This would make an excellent little blog post, but not a "SO good" answer. Would explain the downvote! – Manicotti

Answer 7

Another way is to add one of the local repositories as a remote to another one.

$ cd repo1
$ git remote add repo2 file:///path/to/repo2/.git

So that you can fetch branches, rebase local branches, or cherry-pick commits from one local repo to another.

$ git remote update repo2
$ git fetch repo2 branch:branch-from-repo2
$ git log branch-from-repo2

Actinium