git-from-the-bottom-up VS Git

Here's a great walk through for how Git works from the bottom up: https://jwiegley.github.io/git-from-the-bottom-up/

It's short, easy to understand and you'll understand HEAD.

Very tangential:

Gerrit also stores some of its configs in a git repo. I was setting up a new instance, but couldn't get Admin permissions because the way my auth front-end didn't play well with the docker image's assumptions.

Gerrit already does a lot of its work via non-standard references. For example, you don't push to a branch, `refs/branches/foo`, you push to a separate `refs/for/foo` namespace that creates the review.

Similarly, Group config is stored in the All-Users git repo [1], but in references created after a UUID, in `refs/groups/UU/UUID`.

I ended up having a to exercise the plumbiest of plumbing commands [2] to create a new commit from scratch (from a tree, from the index, from blobs), to update the group ref to add myself to the Administrators group (this, of course, requires a local shell and permissions on the Gerrit host). It was a great way to exercise what I had learned in Git from the Bottom Up [3]

[1] https://gerrit-review.googlesource.com/Documentation/config-...

[2] https://git-scm.com/book/en/v2/Git-Internals-Git-Objects

[3] https://jwiegley.github.io/git-from-the-bottom-up/

I found Git from the Bottom Up helpful. It is very short as well. Then refer to the official book when you want more detail.

I recently came across "Git from the Bottom Up by John Wiegley" (thanks to Coding Blocks podcast), he has a chapter about rebasing: https://jwiegley.github.io/git-from-the-bottom-up/1-Repository/7-branching-and-the-power-of-rebase.html

You won't have to put your entire life on break in order to understand the fundamentals of git and why it works the way it works. Going through https://jwiegley.github.io/git-from-the-bottom-up/ and really understanding the material will take you a couple of hours at max, but will save you a lot of time in the future.

Wanting to understand things before using them is hardly elitism, not sure why you would think that.

Just like you probably don't want to fix bugs without understand the cause, it's hard to use a tool correctly unless you know how the tool works.

Boy, I can't find this either (but also, the kernel mailing list is _really_ difficult to search). I really remember Linus saying something like "it's not a real SCM, but maybe someone could build one on top of it someday" or something like that, but I cannot figure out how to find that.

You _can_ see, though, that in his first README, he refers to what he's building as not a "real SCM":

https://github.com/git/git/commit/e83c5163316f89bfbde7d9ab23...

Here is the direct link, as HN somehow removes the query string: https://github.com/git/git/commits?author=peff&since=2023-10...

I understand all that.

I'm saying, if you write a survey and one of the possible answers is "diff", but you don't clearly define what you mean by "diff", then don't be surprised if respondents use any reasonable definition that makes sense to them. Ask an ambiguous question, get a mishmash of answers.

The thing that Git uses for packfiles is called a "delta" by Git, but it's also reasonable to call it a "diff". After all, Git's delta algorithm is "greatly inspired by parts of LibXDiff from Davide Libenzi"[1]. Not LibXDelta but LibXDiff.

Yes, how Git stores blobs (using deltas) is orthogonal to how Git uses blobs. But while that orthogonality is useful for reasoning about Git, it's not wrong to think of a commit as the totality of what Git does, including that optimization. (Some people, when learning Git, stumble over the way it's described as storing full copies, think it's wasteful. For them to wrap their heads around Git, they have to understand that the optimization exists. Which makes sense because Git probably wouldn't be practical if it lacked that optimization.)

The reason I'm bringing all this up is, if you're trying to explain Git, which is what the original article is about, then it's very important to keep in mind that someone who is learning Git needs to know what you mean when you say "diff". Most people who already know Git would tend to gravitate toward the definition of "diff" that you're assuming (the thing that Git computes on the fly and never stores), but people who already know Git aren't the target audience when you're teaching Git.

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[1] https://github.com/git/git/blob/master/diff-delta.c

Didn't Git have a new default merge strategy, `ort` https://github.com/git/git/blob/master/Documentation/RelNote... ?

Yes, but you are referring to standalone scripts, not functions defined within a Bash script.

Compare for example the following helper code used for git command completion inside Bash and inside PowerShell.

Bash: https://github.com/git/git/blob/master/contrib/completion/gi...