How HEAD works in git
Hello! The other day I ran a Mastodon poll asking people how confident they were that they understood how HEAD works in Git. The results (out of 1700 votes) were a little surprising to me: 10% “100%” 36% “pretty confident” 39% “somewhat confident?” 15% “literally no idea” I was surprised that people were so unconfident about their understanding – I’d been thinking of HEAD as a pretty straightforwa
Popular git config options
Hello! I always wish that command line tools came with data about how popular their various options are, like: “basically nobody uses this one” “80% of people use this, probably take a look” “this one has 6 possible values but people only really use these 2 in practice” So I asked about people’s favourite git config options on Mastodon: what are your favourite git config options to set? Right now
Inside .git
Hello! I posted a comic on Mastodon this week about what’s in the .git directory and someone requested a text version, so here it is. I added some extra notes too. First, here’s the image. It’s a ~15 word explanation of each part of your .git directory. You can git clone https://github.com/jvns/inside-git if you want to run all these examples yourself. Here’s a table of contents: HEAD: .git/head b
Do we think of git commits as diffs, snapshots, and/or histories?
Hello! I’ve been extremely slowly trying to figure how to explain every core concept in Git (commits! branches! remotes! the staging area!) and commits have been surprisingly tricky. Understanding how git commits are implemented feels pretty straightforward to me (those are facts! I can look it up!), but it’s been much harder to figure out how other people think about commits. So like I’ve been do
Some notes on NixOS
Hello! Over the holidays I decided it might be fun to run NixOS on one of my servers, as part of my continuing experiments with Nix. My motivation for this was that previously I was using Ansible to provision the server, but then I’d ad hoc installed a bunch of stuff on the server in a chaotic way separately from Ansible, so in the end I had no real idea of what was on that server and it felt like
git branches: intuition & reality
Hello! I’ve been working on writing a zine about git so I’ve been thinking about git branches a lot. I keep hearing from people that they find the way git branches work to be counterintuitive. It got me thinking: what might an “intuitive” notion of a branch be, and how is it different from how git actually works? So in this post I want to briefly talk about an intuitive mental model I think many p
Confusing git terminology
Hello! I’m slowly working on explaining git. One of my biggest problems is that after almost 15 years of using git, I’ve become very used to git’s idiosyncracies and it’s easy for me to forget what’s confusing about it. So I asked people on Mastodon: what git jargon do you find confusing? thinking of writing a blog post that explains some of git’s weirder terminology: “detached HEAD state”, “fast-
Behind "Hello World" on Linux
Today I was thinking about – what happens when you run a simple “Hello World” Python program on Linux, like this one? print("hello world") Here’s what it looks like at the command line: $ python3 hello.py hello world But behind the scenes, there’s a lot more going on. I’ll describe some of what happens, and (much much more importantly!) explain some tools you can use to see what’s going on behind
Why is DNS still hard to learn?
I write a lot about technologies that I found hard to learn about. A while back my friend Sumana asked me an interesting question – why are these things so hard to learn about? Why do they seem so mysterious? For example, take DNS. We’ve been using DNS since the 80s (for more than 35 years!). It’s used in every website on the internet. And it’s pretty stable – in a lot of ways, it works the exact
Introducing "Implement DNS in a Weekend"
Hello! I’m excited to announce a project I’ve been working on for a long time: a free guide to implementing your own DNS resolver in a weekend. The whole thing is about 200 lines of Python, including implementing all of the binary DNS parsing from scratch. Here’s the link: This project is a fun way to learn: How to parse a binary network protocol like DNS How DNS works behind the scenes (what’s ac
Writing Javascript without a build system
Hello! I’ve been writing some Javascript this week, and as always when I start a new frontend project, I was faced with the question: should I use a build system? I want to talk about what’s appealing to me about build systems, why I (usually) still don’t use them, and why I find it frustrating that some frontend Javascript libraries require that you use a build system. I’m writing this because mo
Why does 0.1 + 0.2 = 0.30000000000000004?
Hello! I was trying to write about floating point yesterday, and I found myself wondering about this calculation, with 64-bit floats: >>> 0.1 + 0.2 0.30000000000000004 I realized that I didn’t understand exactly how it worked. I mean, I know floating point calculations are inexact, and I know that you can’t exactly represent 0.1 in binary, but: there’s a floating point number that’s closer to 0.3
Examples of floating point problems
Hello! I’ve been thinking about writing a zine about how things are represented on computers in bytes, so I was thinking about floating point. I’ve heard a million times about the dangers of floating point arithmetic, like: addition isn’t associative (x + (y + z) is different from (x + y) + z) if you add very big values to very small values, you can get inaccurate results (the small numbers get lo
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The "current branch" in git
Some notes on nix flakes
In a git repository, where do your files live?
Notes on using a single-person Mastodon server
How do Nix builds work?
Some notes on using nix
Examples of problems with integers