[exec] Add new command

[Saphyel]

Implementation of #1907 part 1

This command execute an external command, the idea is provide similar functionality to phing

Example of usage:

drupal exec "ls -al"

[Saphyel]

@enzolutions recommended follow this approach

[novia713]

@Saphyel i see you're using Symfony\Component\Process\Process;
perhaps you ought use the already existent /src/Utils/ShellProcess.php

it in fact also uses Process() but it also shows a percent advance graphic ....
it was developed for showing advance in composer calls, but should be usable also in any command
i'm not sure, perhaps ShellProcess is not ideal for you, but i thinked you should know it ....

[novia713]

i was being thinking about this.
i suggest you @Saphyel to use the existing ShellProcess, to avoid duplication
perhaps you should refactor or add more options (to not show the progress bar) to ShellProcess
i did that, ping me anytime if you want talk about this

[Saphyel]

@novia713 I'll try to do it later today, I really appreciate your comments! ^^ I'm learning more than I thought with this PR!

[Saphyel]

@novia713 take a look now! 💃

[Saphyel]

By the way I fixed the output of --composer:

[novia713]

yes, i was aware of that lack of linebreak in between the progress bar & the info message.
i lived very sad these late days because of it, now i'm happy !! 👯

[novia713]

reminder for @novia713 (myself) to open an issue to change «shellexec_output» key name in config.yml in favour of «composer_output» when this PR were merged

[jmolivas]

@Saphyel PR was merged. This will be included on next release, Thanks.

@novia713 Thanks for helping to test and commenting.