Git: under the basics

My boss told me that my goal in this quarter is to working on Continuous Integration for our current product, and all of a sudden I think there’s a lot of gap between the goal and my current skill. The first thing came into my mind is that: “Ohhh, I am still not quite familiar with Git”. After a short period of panic, I sit down to learn about git. And here’s my note.

If you think you could learn git with manual after you learn how to branch, commit and merge, then you might probably be dispointted. Git is very flexible but it do something in a more novel way, so certain understanding of it’s internal is necessary for mastering it, and would be helpful when you look for help in manual. For example, I hear about so many terms such as “HEAD”, “Index”, “Ref”, “Staging Area”, but I could not tell exactly what is that, and I don’t even know how git works. After some diving, I wrapped something very basic in this post.

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Sync two Git remote repositories

In Yahoo we use Gerrit as our code review tool. Engineers commit code changes to Gerrit for review. After code has been reviewed by peers, Gerrit help push to Github. However sometimes bad thing happens.

For example, if a committer forget to setup Gerrit env and the code is committed and pushed to Github directly (because he has this permission to do so), he will notice this soon because future changes from Gerrit might break. Then he try to submit a review for the missing commit to Gerrit with an “git commit —amend” to generate a change-id (which is used by Gerrit). Because “—amend” generate different commit-id, so after the review is passed, even the content is the same, the commit-id in two remote repo (Gerrit and Github) is different, which leads to future reviews are still not able to pushed to Github from Gerrit and sometimes new review could not be submitted.

So how could we fix it? It would be a good idea to push changes from Github to Gerrit to get them in sync. Here are two options.

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