[init] add _corral and _repo folders to .gitignore

[ghost]

It's stated in the Getting started using Corral section of the README.md to add the folder _corral and _repo to the .gitignore file. I think this can be done by the init command that is described ealier in the README.md

So far init doesn't create it's own project folder and that's why I think this behavior should be hidden behind a CLI flag before making it the default behavior.

[rhagenson]

I was the one who suggested those additions to README so I will voice my opinion on this.

I think it should only add the lines iff .gitignore exists already. On that point, it definitely should be a flag, not on by default so we are not forcing a user into undoing work just because they wanted corral init. If .gitignore is present and the flag is given, I see no reason why we cannot safety assume Git is used and the user wants corral folders to be ignored.

My other thought on the matter though is I would typically run corral init then git init, so then in order for corral to add to .gitignore it would have to create the file, or the user would have to run the two inits in reverse of what I would expect AND create a .gitignore (likely blank).

@fibric How did you see this working with respect to the order of steps a user goes through?

[ghost]

Corral won't find a .gitignore file no matter the order of execution.
git init doesn't create a .gitignore file unless u set up a git template folder and configure git to use the template folder like so git config --global init.templatedir /path/to/template

I think Corral can check for the presence of the .git folder which exists after git init is executed. When executing Corral with parameter i.e. --with-git it can create (if-missing) the .gitignore file and append _corral and _repos.

If https://github.com/ponylang/library-scaffolding-generator is still alive, it also could care about the .gitignore file. It already creates the file and writes some content to it. But I think Corral is still the better place to care about Corral related gitignore entries.

[SeanTAllen]

Closing.

Creation of a default .gitignore should be part of #147 when it is implemented.