# Contributing to coreutils

Contributions are very welcome, and should target Rust's main branch until the
standard libraries are stabilized. You may *claim* an item on the to-do list by
following these steps:

1. Open an issue named "Implement [the utility of your choice]", e.g. "Implement
   ls".
1. State that you are working on this utility.
1. Develop the utility.
1. Add integration tests.
1. Add the reference to your utility into Cargo.toml and Makefile.
1. Remove utility from the to-do list in the README.
1. Submit a pull request and close the issue.

The steps above imply that, before starting to work on a utility, you should
search the issues to make sure no one else is working on it.

## Best practices

1. Follow what GNU is doing in terms of options and behavior. It is recommended
   to look at the GNU Coreutils manual ([on the
   web](https://www.gnu.org/software/coreutils/manual/html_node/index.html), or
   locally using `info <utility>`). It is more in depth than the man pages and
   provides a good description of available features and their implementation
   details.
1. If possible, look at the GNU test suite execution in the CI and make the test
   work if failing.
1. Use clap for argument management.
1. Make sure that the code coverage is covering all of the cases, including
   errors.
1. The code must be clippy-warning-free and rustfmt-compliant.
1. Don't hesitate to move common functions into uucore if they can be reused by
   other binaries.
1. Unsafe code should be documented with Safety comments.
1. uutils is original code. It cannot contain code from existing GNU or Unix-like
   utilities, nor should it link to or reference GNU libraries.

## Commit messages

To help the project maintainers review pull requests from contributors across
numerous utilities, the team has settled on conventions for commit messages.

From http://git-scm.com/book/ch5-2.html:

```
Short (50 chars or less) summary of changes

More detailed explanatory text, if necessary.  Wrap it to about 72
characters or so.  In some contexts, the first line is treated as the
subject of an email and the rest of the text as the body.  The blank
line separating the summary from the body is critical (unless you omit
the body entirely); tools like rebase can get confused if you run the
two together.

Further paragraphs come after blank lines.

  - Bullet points are okay, too

  - Typically a hyphen or asterisk is used for the bullet, preceded by a
    single space, with blank lines in between, but conventions vary here
```

Furthermore, here are a few examples for a summary line:

* commit for a single utility

```
nohup: cleanup and refactor
```

* commit for a utility's tests

```
tests/rm: test new feature
```

Beyond changes to an individual utility or its tests, other summary
lines for non-utility modules include:

```
README: add help
```

```
uucore: add new modules
```

```
uutils: add new utility
```

```
gitignore: add temporary files
```

## Licensing

uutils is distributed under the terms of the MIT License; see the `LICENSE` file
for details. This is a permissive license, which allows the software to be used
with few restrictions.

Copyrights in the uutils project are retained by their contributors, and no
copyright assignment is required to contribute.

If you wish to add or change dependencies as part of a contribution to the
project, a tool like `cargo-license` can be used to show their license details.
The following types of license are acceptable:

* MIT License
* Dual- or tri-license with an MIT License option ("Apache-2.0 or MIT" is a
  popular combination)
* "MIT equivalent" license (2-clause BSD, 3-clause BSD, ISC)
* License less restrictive than the MIT License (CC0 1.0 Universal)
* Apache License version 2.0

Licenses we will not use:

* An ambiguous license, or no license
* Strongly reciprocal licenses (GNU GPL, GNU LGPL)

If you wish to add a reference but it doesn't meet these requirements, please
raise an issue to describe the dependency.