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Comment by eulenteufel | Hacker News Reader

The quote is kinda wrong in that point 1 and 2 are mixed up. Branches are just pointers to commits. Commits contain a reference to their history. It's only kind of incorrect because in praxis branches are used to refer to a history (a sequence of commits). But it's also misleading once you have to do anything more complicated than just commiting/merging.

When I started out using git I was working with the same assumptions, but I was perpetually confused. Git became a lot easier to use once that misunderstanding cleared up.

Maybe it's just like that for me but I think we might be doing newcomers to git a disservice by explaining the basics of git in this simplified manner.

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Do you have an actual example of this? I've never encountered a situation where those three points are incorrect.

If you're in a detached head state and create a new commit, you have a commit that isn't on a branch. The commit still has a parent, so it's not the branch that's tracking the sequence, it's the commit. Branches are just pointers that get updated as you add commits.

This feels like declaring squares aren't rectangles because you can make rectangles that aren't a square.

Git is only commits. Branches and tags are references to the commits; one moves while the other one doesn’t. That’s it.

Commits link to their parent(s) until the initial commit. You can visualize a “branch” as a series of commits, but the same thing can exist without calling it a branch:

    A -> B -> C —> Initial

Is that a branch? No. How about:

    /refs/heads/main = A

That’s a branch, and it looks exactly the same as a tag:

    /refs/tags/v1 = A

Neither a branch or a tag is “a series of commits” even if you think it does.

> You can visualize a “branch” as a series of commits, but the same thing can exist without calling it a branch

You can visualize a "square" as a rectangle with equal sides, but the same thing can exist without calling it a square.

2. is true or untrue depending on how deeply you interpret it.

A branch is named, points to a commit and under normal circumstances will track the sequence of commits made via itself (i.e. when you commit and HEAD points to branch b, b starts pointing to the child commit). So you could say it's a named sequence of commits.

On the other hand you can reset the branch to any commit in the tree, even ones which aren't even on the current sequence of parents. It is still technically a named sequence of commits, just a totally different one.

Git branch is actually very similar to git tag[1]. For example, there are commands to point branch to completely different commit in different section of the commit graph, just like you can do it with tags.

[1] The main difference perhaps is that, if you create a new commit, the branch pointer will actually be moved to point to that latest commit (while tag stays fixed).

Git supports history rewriting so 1 isn't true. Git uses hashes for "unique ids" hashes aren't unique just low probability of collision, so 3 is also not true.

Having run into issues that appear to be caused by 3 not being true, I don't see that as a theoretical issue.

1 is true. When git is “rewriting” history it’s actually creating a new commits and moving the branch pointer over.

Until the gc reaps them, you can absolutely git checkout the hash of any of the rewritten history and it’s still there, same as you left it. You can even move the branch pointer back, undoing the history rewrite.

So when I do a pull I get their un-rewritten history? Just because they have a short undo buffer doesn't make modifiable history immutable.

> once you have to do anything more complicated than just commiting/merging

If you really have to do more complicated things with git.. why? I mean that seriously, if your workflow necessitates anything more complicated that committing or merging with any level of regularity, it sounds like you have a bad workflow. Committing and merging should be 99.9% of your activity within git, shouldn't it?

It depends a little on how you use git. Apart from stashing (git-stash), I use interactive rebases a lot. Combined with autosquashing it's a very powerful tool to ensure a somewhat nice history.

Of course, this only matters if you care about your history. It feels like there are two camps of git users: One camp squashes every MR/PR together even if it's huge, hasn't heard of git-bisect, creates plenty of merge commits in both directions, and piles unrelated changes into a single commit. The other camp cleanly groups changes into self-contained commits, rebases often resulting in a clean patch-series-style MR/PR, and likes to use git-bisect.

This observation about the two camps rings very true. The sad part is that while the second camp is the original user base of Git, at least GitHub basically acts as if they don't exist and only really caters to the first camp.

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