Is it possible to fetch an Elixir dependency from anywhere other than hex.pm, e.g. github

I am making some changes to an Elixir project to try and make it easier to use in erlang.

I have manage to pull the project from hex but is there any way to declare the source as from gihub.

I can't see how to combine these two lines
```
{AppName, {git, "https://github.com/user/repo", {branch|tag|ref, "string"}}}
```
and
```
{raxx, {elixir, "raxx", "0.15.2"}}
```