How do patches work in Git?

Question

I'm new to Git, but familiar with SVN. As a test I made a repository in a local directory with git init. Then I cloned the empty repository (over SSH using 127.0.0.1, which is another thing I wanted to test) to another local directory. I added some files in repository 2, I did git add * and finally git commit -a -m "First source code".

I now want to create a patch using git format-patch and apply it on repository 1. How do I do this? I know there's a manual, but these things are terribly complicated and make me wanna do certain things to my monitor.

Answer 1

Create your patch via:

$ git format-patch master --stdout > patch.diff

then patch.diff will contain the diff, which you can then send to someone else to apply using:

$ git am < patch.diff

Sometimes, when the manuals are a little dense, it makes sense to look for a tutorial:

http://luhman.org/blog/2009/09/22/git-patch-tutorial

Answer 2

Using GitHub patch

1. Add .patch to a commit URL to get the patch file, example

   github.com/git/git/commit/b6b3b6a.patch

2. Patch the original file like this:

   git am /tmp/b6b3b6a.patch
   

Using GitHub diff

1. Add .diff to a commit URL to get the patch file, example

   github.com/git/git/commit/b6b3b6a.diff

2. Patch the original file like this:

   git apply -p0 /tmp/b6b3b6a.diff
   

§5.3 Distributed Git - Maintaining a Project

Answer 3

You have to go to "repository 2", the one you want to create the patch from, and run git-format-patch to create the patch : git format-patch master --stdout > name_of_patch_file

Then you go in "repository 1", the one you want to apply the patch to : git apply name_of_patch_file

Sometimes it is useful to just check if the patch will cause problems : git apply --check name_of_patch_file

Answer 4

The proper and easier way to do this if you're using Git is via remotes:

cd \path\to\repo1
git remote add otherrepo \path\to\repo2
git fetch otherrepo

git log otherrepo/master  ## Find the commit you want to steal in the list

git cherry-pick SOME_SHA1  ## Snag just one commit
git merge otherrepo/master  ## Merge all of the new commits from otherrepo/master

This will migrate commits from one repo to another, including their authors and commit messages, and will help you sort out merge conflicts (especially if you're moving > 1 commit)

Answer 5

The easiest method to create patches from the last commit (or last few commits) is to use format-patch with a negative number indicating the number of commits to create patches for:

git format-patch -1

You'll get a patch file named after the commit description. The use am to insert it into another repository:

git am << name_of_patch_file