[gioele]

CCAN (C Code Archive Network) http://ccodearchive.net/ follows a similar philosophy. CCAN contains various small, self contained snippet of C code are meant to be be downloaded in a local directory ("vendored") and used directly or with small modifications.

The most straightforward way to use CCAN is to

1) `git clone` it in a subdir;

2) create a `config.h`;

3) include whatever `lib.h` you want in your project.

Updating these micro dependencies means doing `git pull`.

All libraries come with tests and a somewhat standardized API design.

What is missing (compared to your aims) is a declarative way to lock a dependency to a specific version.

[bonkabonka]

Reminds me of [Bob Stout's Snippets](https://github.com/vonj/snippets.org). I used his collection often back when I were a lad.