Erlang git repository dependency from github (undef)

I am trying to run a script that calls

erl -sname egs -pa apps/*/ebin -pa deps/*/ebin -boot start_sasl -s ex_reloader -s egs

I run into this error when calling the script

{"init terminating in do_boot",{undef,[{ex_reloader,start,[],[]},{init,start_it,1,[]},{init,start_em,1,[]}]}}

In my rebar.config files the code goes like this

code for 1st rebar.config

{sub_dirs, [
    "apps/egs",
    "apps/egs_patch",
    "apps/prs"
]}.
{dialyzer_opts, [src, {warnings, [
    behaviours,
    error_handling,
    race_conditions,
    unmatched_returns
%%  underspecs
]}]}.
{erl_opts, [
%%  bin_opt_info,
%%  warnings_as_errors,
    warn_export_all
]}.

Code for 2nd rebar.config

{deps, [
    {ex_reloader, ".*", {git, "https://github.com/extend/ex_reloader.git", "HEAD"}},
    {cowboy, ".*", {git, "https://github.com/extend/cowboy.git", "HEAD"}}
]}.

Is there any reason as to why the repositories are undefined. Should I have other packages installed so git dependency works?

Solution

I figured it out with your help and from another post. I needed to download the rebar library. I used this link to download [1]: http://packages.ubuntu.com/raring/i386/rebar then I used the following commands while in the proper directory.

Add the app to the rebar.config and use:

rebar update-deps

For updating. The first time, you need to use:

rebar get-deps

Then compiled the dependecies, using:

rebar compile

Now, onto the next error...