urbit/CONTRIBUTING.md

# Contributing to urbit

Thank you for your interest in contributing to urbit.

See [urbit.org/docs/getting-started](https://urbit.org/docs/getting-started/#arvo)
for basic orientation and usage instructions.

## Fake ships

You may have an identity on the live network, but doing all your
development on the live network would be cumbersome and unnecessary.
Standard practice in urbit development is to work on a fake `~zod`.
Fake ships use deterministic keys (derived from the ship address)
and don't talk to the live network. They can talk to each other over
the local loopback.

To start a fake ship, simply specify the name with `-F`:

```
$ urbit -F zod
```

You can also pass a name for the *pier* (or ship directory):

```
$ urbit -F zod my-fake-zod
```

To resume a fake ship, just pass the name of the pier:

```
$ urbit fake-zod/
```

## Git practice

Since we use the GitHub issue tracker, it is helpful (though not
required) to contribute via a GitHub pull request. If you already know
what you are doing, skip down to the Style section.

Start by cloning the repository on your work machine:

```
$ git clone https://github.com/urbit/urbit
```

And, additionally, fork the repository on GitHub by clicking the "Fork"
button. Add your fork as a remote:

```
$ git remote add [username] https://github.com/[username]/urbit
```

and set it as the default remote to push to:

```
$ git config --local remote.pushDefault [username]
```

This is good practice for any project that uses git. You will pull
upstream branches from urbit/urbit and push to your personal urbit fork
by default.

Next, start a new branch to do your work on. For `urbit`, please use the
latest tagged release as your starting point. For other repositories,
anywhere pointed to by `master` is alright to start from.

```
$ git checkout -b [branch name] [starting point]
```

Now you are free to do your work on this branch. When finished, you may
want to clean up your commits:

```
$ git rebase -i [starting point]
```

Then you can push to your public fork with `git push` and make a pull
request via the GitHub UI.

After your changes are merged upstream, you can delete your branch (via
github UI or `git push :[branch]` remotely, and with `git branch -d`
locally).

## Style

The urbit project uses two-space indentation and avoids tab characters.
In C code, it should not be too difficult to mimic the style of the code
around you, which is just fairly standard K&R with braces on every
compound statement. One thing to watch out for is top-level sections in
source files that are denoted by comments and are actually indented one
level.

Hoon will be a less familiar language to many contributors. More details
are forthcoming; for now, the `%ford` vane (in 
[`sys/vane/ford.hoon`](https://github.com/urbit/arvo/blob/master/sys/vane/ford.hoon))
is the highest quality code in the kernel.

## Kernel development

Working on either C or non-kernel Hoon should not bring any surprises, but
the Hoon kernel (anything under `sys/` in [urbit/arvo](https://github.com/urbit/arvo))
is bootstrapped from `urbit.pill`, and must be recompiled if any changes are
made. This should happen automatically when you make changes, but if it doesn't,
the command to manually recompile the kernel and install the new kernel
is `|reset` in `dojo`.  This rebuilds from the `sys` directory in the
`home` desk in `%clay`.  Currently, `|reset` does not reload apps like
`dojo` itself, which will still reference the old kernel. To force them
to reload, make a trivial edit to their main source file (under the
`app` directory) in `%clay`.

## The kernel and pills

urbit bootstraps itself using a binary blob called `urbit.pill`. You
probably remember it being fetched from `bootstrap.urbit.org` before
your first boot. This is the compiled version of the kernel (which
you can find in the `sys` directory of [urbit/arvo](https://github.com/urbit/arvo)),
along with a complete copy of the Arvo repository as source.

The procedure for creating `urbit.pill` is often called "soliding". It
is somewhat similar to `|reset`, but instead of replacing your running
kernel, it writes the compiled kernel to a file. The command to solid
is:

```
> .urbit/pill +solid
```

When the compilation finishes, your `urbit.pill` will be found in the
`[pier]/.urb/put/` directory.

You can boot a new ship from your local pill with `-B`:

```
$ urbit -F zod -B path/to/urbit.pill fake-zod
```

Ordinarily, `http://bootstrap.urbit.org/latest.pill` will be updated
to match whatever's on `master` in the `arvo` repository with every
merge to `master`. Older pills will be stored with the first 10
characters of the `git` SHA1 of the relevant commit as `git-[sha1].pill`.

The continuous-integration build of the `urbit/arvo` repository
uploads these pills for any successful build (if the commit or pull-request
affects the `sys/` directory).

You can boot from one of these pills by passing the path to an Arvo
working copy with `-A` (and `-s` for *search*):

```
$ git clone https://github.com/urbit/arvo
$ urbit -F zod -A path/to/arvo -s fake-zod
```

## What to work on

If you are not thinking of contributing with a specific goal in mind,
the GitHub issue tracker is the first place you should look for ideas.
Issues are tagged with a priority and a difficulty. A good place to
start is on either a low-difficulty issue or a low-priority issue.
Higher priority issues are likely to be assigned to someone - if this is
the case, then contacting that person to coordinate before starting to
work is probably a good idea.

There is also a "help wanted" tag for things that we are especially
eager to have outside contributions on. Check here first!

## Staying in touch

Questions or other communications about contributing to Urbit can go to
[support@urbit.org](mailto:support@urbit.org).