Use werl instead of erl when executing iex.bat

[bitwalker]

This is more to start some discussion around this than necessarily the final solution for the problem. This commit sets an environment variable useWerl, which is then checked prior to executing erl in elixir.bat. If it is set to 1, werl is used instead of erl. This allows someone to override it and use erl for iex if they just want to use their native shell for iex (which still works, it's just missing some features like the CTRL+C and CTRL+G menus).

Thoughts?

[josevalim]

@bitwalker unfortunately we cannot use environment variables because if you are inside iex and shell out to an elixir executable (don't ask me why you would do that), the varaible would be set and elixir won't work as expected. I think the best would be to check if +iex is given as argument (we arleady pass it from iex.bat) and then act accordingly. What do yu think?

[bitwalker]

Ah that does make sense, hadn't considered that. I like your idea. I'll push an update for that shortly.

[josevalim]

Btw, thanks for looking into this. I think that, if we change it to use werl, we can also change it to use the proper the smart shell. Theoretically we just need to pass the --erl "-user Elixir.IEx.CLI" (and guarantee it comes after -noshell in elixir.bat). As we do here:

https://github.com/elixir-lang/elixir/blob/master/bin/iex#L42

[bitwalker]

I'll test that out as well while I'm in there

[bitwalker]

@josevalim Ok, this actually works a lot better now with that last change. Let me know what you think.

[josevalim]

This is a dream coming true! Thank you!

[bitwalker]

Thanks José!