How do I update a GitHub forked repository?

4073

I recently forked a project and applied several fixes. I then created a pull request which was then accepted.

A few days later another change was made by another contributor. So my fork doesn't contain that change.

How can I get that change into my fork? Do I need to delete and re-create my fork when I have further changes to contribute? Or is there an update button?

This question is tagged with git github updates pull-request git-fork

~ Asked on 2011-08-30 13:53:00

The Best Answer is


4607

In your local clone of your forked repository, you can add the original GitHub repository as a "remote". ("Remotes" are like nicknames for the URLs of repositories - origin is one, for example.) Then you can fetch all the branches from that upstream repository, and rebase your work to continue working on the upstream version. In terms of commands that might look like:

# Add the remote, call it "upstream":

git remote add upstream https://github.com/whoever/whatever.git

# Fetch all the branches of that remote into remote-tracking branches

git fetch upstream

# Make sure that you're on your master branch:

git checkout master

# Rewrite your master branch so that any commits of yours that
# aren't already in upstream/master are replayed on top of that
# other branch:

git rebase upstream/master

If you don't want to rewrite the history of your master branch, (for example because other people may have cloned it) then you should replace the last command with git merge upstream/master. However, for making further pull requests that are as clean as possible, it's probably better to rebase.


If you've rebased your branch onto upstream/master you may need to force the push in order to push it to your own forked repository on GitHub. You'd do that with:

git push -f origin master

You only need to use the -f the first time after you've rebased.

~ Answered on 2011-08-30 14:01:26


783

Starting in May 2014, it is possible to update a fork directly from GitHub. This still works as of September 2017, BUT it will lead to a dirty commit history.

  1. Open your fork on GitHub.
  2. Click on Pull Requests.
  3. Click on New Pull Request. By default, GitHub will compare the original with your fork, and there shouldn't be anything to compare if you didn't make any changes.
  4. Click switching the base if you see that link. Otherwise, manually set the base fork drop down to your fork, and the head fork to the upstream. Now GitHub will compare your fork with the original, and you should see all the latest changes. enter image description here
  5. Create pull request and assign a predictable name to your pull request (e.g., Update from original).
  6. Scroll down to Merge pull request, but don't click anything yet.

Now you have three options, but each will lead to a less-than-clean commit history.

  1. The default will create an ugly merge commit.
  2. If you click the dropdown and choose "Squash and merge", all intervening commits will be squashed into one. This is most often something you don't want.
  3. If you click Rebase and merge, all commits will be made "with" you, the original PRs will link to your PR, and GitHub will display This branch is X commits ahead, Y commits behind <original fork>.

So yes, you can keep your repo updated with its upstream using the GitHub web UI, but doing so will sully your commit history. Stick to the command line instead - it's easy.

~ Answered on 2014-05-25 07:31:20


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