README.md

Get list of Coq package repos at `gl.mathhub.info`
(using [httpie](https://httpie.io)):
```bash
http -F gl.mathhub.info/api/v4/groups/108/projects?per_page=100 > coq_projects.json
```

Get list of SSH repo urls:
```bash
jq '.[] | .ssh_url_to_repo' coq_projects.json > coq_submodule_urls
```

Manually remove the following repos from `coq_submodule_urls`:
- `color`: Too much non-Coq package data (~ 100GB)
- `coq.8.9.0`: Main Coq repo
- `documentation`: Not a Coq package
- `foundation`: Source directory broken
- `geocoq`: Empty repo
- `math-classes`: Empty repo

Create a submodule for each remaining entry in `coq_submodule_urls`:
```bash
xargs -n1 git submodule add < coq_submodule_urls
```