A rebar plugin
$ rebar3 compile
Add the plugin to your rebar config:
{plugins, [
{ rebar3_elmer, ".*", {git, "git@host:user/rebar3_elmer.git", {tag, "0.1.0"}}}
]}.
Then just call your plugin directly in an existing application:
$ rebar3 rebar3_elmer
===> Fetching rebar3_elmer
===> Compiling rebar3_elmer
<Plugin Output>