Line endings on Docker

[felipecrs]

Currently, if you use Argbash Docker, it warns you in case it doesn't find a -o option because it would return the output with CRLF line endings instead of LF.

But in fact, Docker only outputs CRLF if you use -it. If you use docker run --rm matejak/argbash, it will return LF line endings.

The question is: is -it really needed (because of the interactive terminal)? If yes, is it only needed on argbash-init? If yes again, it should be only included in the argbash-init docker shim so. And then, we could remove this validation in the entrypoint.sh.