jakstys.lt/content/log/git-subtrac.md

---
title: "git-subtrac and Zig"
date: 2022-04-23T05:37:51+03:00
draft: true
---

TLDR: I wish plain `git clone <repository>` would check out submodules if they
are in the same repository.

I use [`git-subtrac`][git-subtrac] for some of my projects, and am not very
enthusiastic about Zig getting it's own package manager (can we all use
git-subtrac and be done with it?). A few weeks ago in a park in Milan my
conversation with [Andrew Kelley](https://andrewkelley.me/) was something like:

- me: "git-subtrac yadda yadda yadda submodules but better yadda yadda yadda".
- Andrew: "if I clone a repository that uses git-subtrac with no extra
  parameters, will it work as expected?"
- me: "no, you have to pass `--recursive`, so git will checkout submodules...
  even if they are already fetched."
- Andrew: "then it's a piece-of-shit-approach."

Uh, I agree. People have not grown muscle memory to clone repositories with
`--recursive` flag and never will, so it's impossible to adopt git-subtrac
beyond well-controlled silos. Which is why we will have a
yet-another-programming-language-specific-package-manager, this time for zig.
Or at least my argument for using git-subtrac stops right there.

Why git-subtrac?
----------------

[`git-subtrac`][git-subtrac] is like "classic" git submodules, but all refs of
the dependencies stay in the same repository. Wait, stop here. Repeat after me:
_it is git submodules, but all refs stay in the same repository_. I also call
it "good vendoring". Since all the deps are in our repo, no external force can
make our dependency unavailable.

It is, howerver, harder to *add* a dependency with submodules than with, say,
`go get <dependency>`. Let's talk about adding dependencies.

Adding dependencies
-------------------

All of the programming languages I've used professionally whose name does not
start with "c"[^1]  have package managers[^2], which make "dependency
management" easy. These package managers will download and build the dependency
tree, sometimes conveniently generate a "lock file", so your project has an
illusion of being "reproducible".

C/C++ projects I've been involved usually had 1-5 non-system dependencies,
whereas all others -- tens or hundreds. This uncovers an obvious correlation:
if it's easy to add dependencies, they will be added. En masse. Not adding
dependencies in Go/Python/whatever requires discipline. Slip once, add some
crap -- it will be very hard to remove, as changing dependencies often require
large rewrites. Not adding dependencies in C/C++, however, is the path of least
resistance. However, in the long term, my C/C++ projects tended to survive
longest (or required least amount of changes to build and run after the world
moved on) just because of this.

Making it easy to depend on external code is is convenient during development,
but frees (or denies, depending how one looks at it) developers from their
basic right (or obligation?) to understand them. And adds real long-term
maintenance costs.

To sum up, the "modern" languages optimize for initial development experience,
not maintenance. And as [Corbet says][linux-rust]. "We can't understand why
Kids These Days just don't want to live that way". Kids want to build, John,
not maintain. This house is in desperate need of maintenance, but my son
refuses to do so, and builds a new car instead.

{{<img src="https://dl.jakstys.lt/mtpad/house.jpg"
    alt="House of Duplo pieces"
    caption="House of Duplo pieces"
    width="50%"
    >}}

This is why I am always hesitant to pull in code to my project, and have a my
dependency checklist:

- Obvious: does it work at all?
- How easy is it to build, run and run it's tests?
- Is it well written? API surface, documentation, tests, error handling, error
  signaling, logging, metrics (if applicable), etc.
- It's system dependencies.
- It's transitive dependencies.

Zooming into the last part: C projects tend to do it well. For Go and Python
projects a small number of dependencies is often a sign of care and quality on
other areas, too. [mattn/go-sqlite3](https://github.com/mattn/go-sqlite3),
[google/brotli](https://github.com/google/brotli),
[apenwarr/redo](https://github.com/apenwarr/redo),
[cmph](http://cmph.sourceforge.net/) are good examples.

If a dependency is well written, but has more transitive dependencies than I
need and there is no good alternative, I will fork it and remove unnecessary
code and dependencies. My recent example is
[sql-migrate](https://github.com/motiejus/sql-migrate).

If I may combine Corbet's views with mine: if we understand and audit our
dependencies (and transitive ones), we will have less dependencies and a more
maintainable system. Win-win.

Which brings us to...

Transitive dependencies and git-subtrac
---------------------------------------

[`git-subtrac`][git-subtrac] does not deal with transitive dependencies. At
least not directly. Or I am not aware of it. Ok, I haven't tried.

If we audit and thus understand our dependencies, we will be able to add
transitive ones to our project even without support of git-subtrac. So perhaps
git-subtrac shouldn't care?

Conclusion
----------

Can git checkout local submodules when they are in the same repository, so our
conversation of reconsidering (or not having) a zig package manager doesn't
stop after 5 seconds?

[^1]: Alphabetically: Erlang, Go, Javascript, PHP, Perl, Python.
[^2]: Usually written in the same language. Zoo of package managers (sometimes
  a couple of popular ones for the same programming language) is a can of worms
  in an on itself worth another blog post.

[git-subtrac]: https://github.com/apenwarr/git-subtrac/
[linux-rust]: https://lwn.net/SubscriberLink/889924/a733d6630e3b5115/