Adventures in brine

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A punnet size guide to Git cherry picking

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I'd just finished a load of work on a project. I'd made my commit and was a about to push to origin, when I noticed I was on the wrong branch.

What a numpty.

Why this happened, is probably a good subject for another post. What I want to talk about is how I resolved the issue.

Sitrep

The situation was that I had two branches; develop, my intended branch and wrong-branch, the branch I actually committed to. wrong-branch was the product of bad practice on my part, luckily it was up-to-date with develop, give or take a couple of small amends. wrong-branch had itself a number of commits, in amongst merges from the develop, that I didn't want merging back into develop.

----------------        develop
    \----\-----\---        wrong-branch

Ideally, I wanted to pick the very last commit on wrong-branch and append it to end of develop. The contents of the commit was mostly in isolation of the rest of the project, so I didn't expect any conflicts.

Precautions

So, what did I do? Firstly, I took two precautionary steps:

1. Update wrong-branch with develop

I wanted to reduce the risk of conflict, so I made sure wrong-branch had the latest updates from develop.

git checkout wrong-branch
git merge develop

2. Made a copy of develop, in case anything went wrong

git checkout develop
git checkout develop-tmp

First crack

Did I mention, that this is the first time I've attempted a cherry pick? In order to perform a cherry pick, you need the hash of the commit you want to grab. The hash will look something like d736fa95b41a36f5c59074afdbc773d60ca5a99b, or the shortened version d736fa9. You can get this from git log.

git checkout develop-tmp
git cherry-pick d736fa9

The second line of the example above resulted in the following error:

... is a merge but no -m option was given.

Getting it right

The -m option allows for a parent number. A commit's parent is essentially the commit's predecessor, usually the commit that spawned the current commit. On a branch, the parent number starts at 1, and increases as you go back along the tree. So, if you wanted to append the commit to the end of the branch, use '-m 1'.

Let's give it another go:

git checkout develop-tmp
git cherry-pick -m 1 d736fa9

Huzzah! It worked. If you had any conflicts at this point, now is the time to resolve and commit. Then, all that is left, is to merge into the primary develop branch.

git checkout develop
git merge develop-tmp
git branch -D develop-tmp

The end.

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