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Git Essentials


All students recently graduated from Computer Science college know about AI, Database, System and Algorithm, but rare of them know about Git more than git commit and git merge. When I have to work with them, and review their code, the messy commit history makes me crazy. So here it is, the Git essentials I want my colleagues to know.

Don’t pull it, fetch it

Every morning you come to the office, the first thing you should do is catching up with the latest code. But do NOT git pull it. Actually git pull = git fetch + git merge. In other words, git pull will perform git merge automatically, which might probably mess up the commit history, if not cause conflicts.

Instead, git fetch only fetch the remote and update the remote branch on your local git repository (say origin/main). Then you need to scan the commit history, get to know what is going on and decide how to deal with it.

Don’t merge it, rebase it

A common workflow is, creating a new branch (from main branch), doing something on it (with one or more commits), and then opening a PR (Pull Request) or MR (Merge Request) to ask for review. But often, the main branch has been updated by others since our branch is created. So we need to update our branch before opening the PR/MR.

Some people will git merge main to update their branch. But this will create a new commit, which is unnecessary and will mess up the commit history. Instead, we should git rebase main to update our branch. This will replay our commits on top of the latest main branch, and keep the commit history clean.

Someone else done the same thing: cherry-pick

You should try to avoid this situation by talking about your plan to your colleagues. But sometimes it just happened. Therefore only parts of commits you want to keep.

Under this situation, you should create a new branch from the latest main branch, and git cherry-pick the commits you want to keep. You will be thankful for yourself if you keep commits atomic and meaningful.

Don’t blame me

Don’t use git blame to blame others (even though it’s named after it). Instead, use git blame to find who is repsonsible for a specific line of code when you want to ask for help. git history -L<start>,<end>:<file> is also good to find the commit history of a specific line of code.

Reference

  1. MIT 6.NULL contains subjects rarely covered in common CS cources, including Git.
  2. GitHub Copilot for CLI includes a powerful command git? used for searching specifically for git invocations.