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Merging Pull Requests

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garyc40 edited this page Jan 9, 2013 · 5 revisions

GitHub provides a built-in feature to merge pull requests automatically, however it is not recommended to use that feature for 2 reasons:

  • Merge bubbles are created. These are the commit messages that go "Merge branch xxx of xxx" right after the last commit of the branch being merged with. These commits cluster up the history.

  • The commit timeline is messed up.

Below is an example, where fork doesn't rebase itself upon the latest development on origin.

A____B___C___D    origin
 \_E___F___G      fork

This is what happens when you merge fork into origin:

A____B___C___D__H     origin
 \_E___F___G___/      fork

Note that H is the merge bubble that we described above. If we do a git log, here's the order of the commits we now have on origin: A E B F C G D H.

That looks really confusing, and you can hardly git bisect through that if that ever becomes necessary.

The proper way to merge pull requests

This would require you to use the git command line.

Let's say you're merging a pull request from a fork: JustinSainton/wp-e-commerce, branch name is ui-improvement. From here on we assume that you set up your local copy using the instructions in Submitting Code. origin is the official WPEC repo.

First, you need to fetch the fork to your local copy

git remote add justin-sainton-fork git@github.com:JustinSainton/WP-e-Commerce.git
git fetch justin-sainton-fork

Checkout a copy of the fork's ui-improvement branch:

git checkout -b pull-request-ui-improvement justin-sainton-fork/ui-improvement

You'll be automatically switched to the local branch you just created off of the fork's remote branch. Now, rebase that local branch upon the WPEC official master (in this case, is the master branch):

git rebase master

If there's any conflict, resolve it. Now switch back to master, and merge with pull-request-ui-improvement

git checkout master
git merge pull-request-ui-improvement

You'll notice that this time, the merge will be "fast-forward", which means there will be no merge bubble, and the time line is preserved (i.e. A B C D E F G, and no H!).

Final step is push master to origin

git push origin master
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