rebar3/README.md

rebar
=====

rebar is an Erlang build tool that makes it easy to compile and  
test Erlang applications, port drivers and releases.

rebar is a self-contained Erlang script, so it's easy to distribute or even  
embed directly in a project. Where possible, rebar uses standard Erlang/OTP  
conventions for project structures, thus minimizing the amount of build  
configuration work. rebar also provides dependency management, enabling  
application writers to easily re-use common libraries from a variety of  
locations (git, hg, etc).

Building
--------

Information on building and installing Erlang/OTP can be found
in the `INSTALL.md` document.

### Dependencies

To build rebar you will need a working installation of Erlang R13B03 (or
later).

Should you want to clone the rebar repository, you will also require git.

#### Downloading

Clone the git repository:

    $ git clone git://github.com/basho/rebar.git

#### Building rebar

    $ cd rebar/
    $ ./bootstrap
    Recompile: src/getopt
    ...
    Recompile: src/rebar_utils
    ==> rebar (compile)
    Congratulations! You now have a self-contained script called "rebar" in
    your current working directory. Place this script anywhere in your path
    and you can use rebar to build OTP-compliant apps.


Contributing to rebar
=====================

Coding style
------------

Do not introduce trailing whitespace.

Do not introduce lines longer than 80 characters.

### Indentation

To have consistent indentation we have vi modeline/emacs local variable  
headers in rebar's source files. This works automatically with vi.  
With Emacs you have to declare <code>'erlang-indent-level</code>
set to <code>4</code>  
as a safe local variable value. If not configured Emacs will prompt  
you to save this as part of custom-set-variables:

    '(safe-local-variable-values (quote ((erlang-indent-level . 4))))
You can also tell Emacs to ignore file variables:

    (setq enable-local-variables nil
          enable-local-eval nil)


Writing Commit Messages
-----------------------

Structure your commit message like this:

<pre>
One line summary (less than 50 characters)

Longer description (wrap at 72 characters)
</pre>

### Summary

* Less than 50 characters
* What was changed
* Imperative present tense (fix, add, change)
> Fix bug 123  
> Add 'foobar' command  
> Change default timeout to 123  
* No period

### Description

* Wrap at 72 characters
* Why, explain intention and implementation approach
* Present tense

### Atomicity

* Break up logical changes
* Make whitespace changes separately

Dialyzer and Tidier
-------------------

Before you submit a patch check for discrepancies with
[Dialyzer](http://www.erlang.org/doc/man/dialyzer.html):

<pre>
$ cd rebar/
$ ./bootstrap debug
$ dialyzer ebin -Wunmatched_returns -Werror_handling -Wrace_conditions -Wunderspecs
</pre>

The following discrepancies are known and safe to ignore:
<pre>
rebar_templater.erl:249: The call rebar_templater:consult(
                                Cont1::erl_scan:return_cont(),'eof',
                                Acc::[any()])
                         contains an opaque term as 1st argument when terms
                         of different types are expected in these positions
rebar_utils.erl:144: Call to missing or unexported function escript:foldl/3
rebar_utils.erl:165: The created fun has no local return
</pre>

It is **strongly recommended** to check the code with
[Tidier](http://tidier.softlab.ntua.gr:20000/tidier/getstarted).  
Select all transformation options and enable **automatic**
transformation.  
If Tidier suggests a transformation apply the changes **manually**
to the source code.  
Do not use the code from the tarball (*out.tgz*) as it will have
white-space changes  
applied by Erlang's pretty-printer.