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Copilot Lvl 2
Message 1 of 2

Why doesn't git keep track of parent branches?

We are trying to set up a way to have the pull request default to the correct branch (which is the parent one 95% of the time).  While trying to do this, I inevidably come across the reality that there is not a greate way to get the parent branch of a branch.  The reason why this is hard is that a branch is just a pointer to a commit, and a commit may have multiple or no parents.  What I don't understand is why a branch is only a pointer to a commit?  It would seem useful to also track an additional piece piece of data that would point to a parent branch, and when you create a new branch with checkout -b, it would get the current branch you are in and set that as the parent of the new branch.  If you are merging branches, there would be multiple parents of the commit, but the branch and parent branch would still stay the same as it was before the merge.  Is there some design reason why this information is not stored?  If not, is there some reason the git community wouldn't accept this sort of change?

1 Reply
Community Manager
Message 2 of 2

Re: Why doesn't git keep track of parent branches?

This is an interesting idea. You said:

 

  • why a branch is only a pointer to a commit?
  • seem useful to also track an additional piece piece of data that would point to a parent branch, and when you create a new branch with checkout -b, it would get the current branch you are in and set that as the parent of the new branch.

 

How would you change the definition of a branch so that you can always get the parent branch even if:

 

  • The parent branch is deleted
  • The parent branch and the child branch diverge completely from the branch point
  • The parent branch is rebased
  • The child branch is rebased
  • etc

 

As for why the branching mechanism is designed the way it is, git's branching mechanism is incredibly lightweight compared to the version control systems that came before it. This is partially because a branch is just a ref. All it takes to create a new branch is to create a tiny file in `.git/refs/heads`.

 

Additionally, the reason why it is designed this way may have to do with git being a distributed version control system. For example, if I execute `git fetch branch-name`, git knows I need to download the set of objects that I do not already have that are directly tied to `branch-name` or any of its parent commits. If we hard-code this parent branch concept, would I also now need to download the set of objects associated with the parent branch? And its parent branch? And its parent branch? And ... ad infinitum?

 

With that said, what problem are you trying to solve by determining the parent branch of a pull request? Perhaps there is something we can suggest if you tell us a bit more?