This is an experimental plugin lets you modify the code path (using add_pathsa/1 and add_pathsz), for a specific set of commands.

You can utilise the plugin by either

1. including it as a rebar dependency
2. installing it into $ERL_LIBS or code:lib_dir
3. putting the source into your plugin_dir directory

Here's an example rebar config:

{path_opts, [

    %% prepend the list of dirs when the compile command is running
    %% NB: the code path is restored immediately after the compile command finishes
    {compile, [{prepend, ["/tmp/foo/ebin"]}]},

    %% append the list of dirs when the xref command runs
    {xref, [
        {append, ["../ebin"]}
    ]}

]}.
{plugins, [rebar_paths_plugin]}.

Take a look in the examples directory to see the xref hook from above in action. You'll need to make sure you run rebar with skip_deps=true in order for xref to not fail on checking the various rebar plugins.

$ cd examples
$ rebar get-deps compile
$ rebar skip_deps=true xref

This plugin is highly experimental and based on rebar features that have not made it into an official rebar branch (and may never do so). You can play with this by looking at this rebar fork/branch:

• https://github.com/hyperthunk/rebar/tree/plugins-rule

which has merged rebar pull requests 129 and 143, which add features this plugin requires in order to work.