Gitlet: Git implemented in JavaScript

http://gitlet.maryrosecook.com/

by fogus • 12 years ago

332 66 12 years ago

gitlet.maryrosecook.com

maryrosecook• 12 years ago

I wrote a short post about how and why I made Gitlet: http://maryrosecook.com/blog/post/introducing-gitlet

rtorr• 12 years ago

Keep making cool stuff. Loved your little lisp project!

317070• 12 years ago

I can't seem to find the rebase code? I've always wondered how that part works. Great work otherwise! I've already taken a look at the three way merger code.

ethomson• 12 years ago

In a nutshell, it checks out the target and cherry-picks what had been HEAD onto it, beginning at the merge-base.

https://github.com/libgit2/libgit2/blob/master/src/rebase.c may be helpful and (hopefully) readable.

albertoleal• 12 years ago

It's pretty awesome of you to provide the annotated source code for Gitlet! :D

brianwillis• 12 years ago

This is the most extreme example of Atwood's law that I've seen so far of.

Any volunteers for making an operating system kernel? Or has that been done already?

bpierre• 12 years ago

There is also js-git [1], a complete implementation of git in JS, founded by two fundraisers [2][3].

[1] https://github.com/creationix/js-git

[2] https://www.kickstarter.com/projects/creationix/js-git

[3] https://www.bountysource.com/teams/js-git/fundraiser

nawitus• 12 years ago

https://github.com/charliesome/jsos

icebraining• 12 years ago

Well, the NetBSD kernel has been ported to JS: http://blog.netbsd.org/tnf/entry/kernel_drivers_compiled_to_...

It's using emscripten, not handwritten JS, though.

agumonkey2• 12 years ago

My favorite emscripten demo was https://blog.mozilla.org/blog/2014/03/12/mozilla-and-epic-pr...

It was really impressive to see UE4 running at ~7 fps on an old ThinkPad (without discrete GPU) in pure software.

dragonwriter• 12 years ago

Any volunteers for making an operating system kernel? Or has that been done already?

Well, there's a PC emulator, http://bellard.org/jslinux/tech.html

skeoh• 12 years ago

Some might also find js-git interesting: https://github.com/creationix/js-git

isxek• 12 years ago

Thanks for posting this. I remembered seeing a similar project before, but I couldn't remember the name.

patcoll• 12 years ago

Kickstarter: https://www.kickstarter.com/projects/creationix/js-git

caipre2• 12 years ago

Sometimes, I can only understand something by implementing it. So, I wrote Gitlet, my own version of Git. I pored over tutorials. I read articles about internals. I tried to understand how API commands work by reading the docs, then gave up and ran hundreds of experiments on repositories and rummaged throught the .git directory to figure out the results.

When the source itself is available, why not just read the code? I understand using articles and documentation to get the high to mid level view, but why not go to the real source of truth if it's available?

nicholasjbs• 12 years ago

I find reading the source of things can be incredibly helpful in some cases, but when I want to really grok something, I need to write code myself. When I'm just reading code it's easy to trick myself into thinking I understand something, but it's much harder to do that if I have to make a piece of code work correctly.

Peter Seibel wrote a great post on code reading, which hits on a similar point: http://www.gigamonkeys.com/code-reading/

caipre2• 12 years ago

I was referring more to the "ran hundreds of experiments" than the "understanding by implementing." I agree wholeheartedly that actually making something reveals far more about a problem/solution than would simply reading about it.

makmanalp• 12 years ago

It's just a different approach - sometimes understanding top-down is easier than bottom-up. The git code is pretty clean and simple, but pedagogically speaking it's not super easy to get an understanding of everything without reading most of it.

It's like reading a math paper where they define all the variables they use first before even getting to the main ideas. It's more rigorous, but not necessarily the most straightforward way to convey something.

Also, you don't necessarily always care that something is a struct or a union or that it's implemented as a custom variant of a B+tree that does xyz or that there's this quirk on Solaris that causes filenames to be written on disk backwards or something.

js2• 12 years ago

Author addresses this: "I went to the actual source to answer a few questions. But doing that was time consuming because I don’t know C well."

Also, the git source isn't the easiest code to follow.

Procrastes• 12 years ago

I really liked your "Git in 600 words.[1]" I think it will help clear up some confusion for some of my VCS wary colleagues.

1. http://maryrosecook.com/blog/post/git-in-six-hundred-words

throwawaymsft• 12 years ago

Not to be rude, but I'm baffled why a professional programmer could be "wary" of using a VCS. Or is it just git in particular? (More understandable, there's a learning curve, but nearly every major project is using it. Git's proven itself.)

jerrysievert• 12 years ago

i once took a leadership position at a small company that had a longtime contractor building one of their core web products out of foxpro. he refused to use any VCS, proclaiming that "version control is for the weak". needless to say, he didn't last very long.

throwawayaway7• 12 years ago

git checkout <branch>

where did my changes go?

recursive• 12 years ago

I think it's git in particular. Git can seem like it has more complexity than is necessary for a version control solution for some arbitrary "simple" project.

greggman• 12 years ago

My favorite "how it works" article is The Git Parable

http://tom.preston-werner.com/2009/05/19/the-git-parable.htm...

willsentance• 12 years ago

I always recommend this: http://nvie.com/posts/a-successful-git-branching-model/

Not exactly a 'how it works' article, more how it can work really well

chx• 12 years ago

My favorite Git tutorial is http://www.sbf5.com/~cduan/technical/git/

you can only really use Git if you understand how Git works. Merely memorizing which commands you should run at what times will work in the short run, but it’s only a matter of time before you get stuck or, worse, break something.

zyxley• 12 years ago

It would be interesting to see this baked into a browser-based text editor. Make it fully client side and you can potentially save the git history in localstorage and use it as an offline web app. I wonder if there are any git servers that support websockets...

teraflop• 12 years ago

No need for websockets. Git has supported pushing and pulling via HTTP for many years.

azeirah• 12 years ago

You don't need git for that, simply save every keystroke made by the user.

WickyNilliams• 12 years ago

Can't tell if you mean overwriting after every keystroke (if so, no history); or saving a "fresh copy" after each keystroke (history, but terribly inefficient - localStorage has space limitations); or saving a series of diffs (how far do you have to go down that path before you realise you should have just used git?)

Sir_Cmpwn• 12 years ago

I've asked GitHub to enable CORS for their https git endpoints, and I'm not the first. Email them at support@github.com if you can think of some cool stuff to do with that enabled.

filearts• 12 years ago

This is a collossal effort and a huge community service. Thank you for being so thorough in documenting your work. Even if others don't directly use your code, you have given the world a great template to understand and implement git!

hyp0• 12 years ago

A related way to learn is from git's initial source, which was quite small. https://news.ycombinator.com/item?id=8650483

Warning: the file format has changed slightly.

jokoon• 12 years ago

how are files handled ?

joelthelion• 12 years ago

What are the expected use cases?

gitspirit3• 12 years ago

One obvious use case is being able to edit files and have them saved to your git repo without leaving the browser.

bmj• 12 years ago

From TFA:

I wrote Gitlet to explain how Git works. I didn't write it to be used. It would be unwise to use Gitlet to version control your projects.

nhlx2• 12 years ago

Why JavaScript?

robotnoises• 12 years ago

Atwood's law?

phatak-dev• 12 years ago

Superb effort.

gitspirit3• 12 years ago

git is a tool that have to be introduced to as many as possible, even non-developers. In essence git is a fundamental part of the future global world collaboration. One can't overestimate the gits value.

eyko• 12 years ago

One can't overestimate the gits value

I think you just did that.

gitspirit3• 12 years ago

In my world I haven't

zrail• 12 years ago

OT: I love the typography on your site, especially the little touches like the decenders overlapping link underlines.

edit: after some research turns out the link underline styling is a Safari thing. My point stands, though, the typography is wonderful.

Gitlet: Git implemented in JavaScript

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