git: mimic --branch and --single-branch git clone flags

[caarlos0]

I was looking into having something similar as git clone --branch foo --single-branch on kaniko.

The main difference is that git's --branch allows for both a branch or a tag, and you don't have to know which one it is beforehand.

I was playing around with some code and found a way to implement it in go-git inspired by git's source code: go-git/go-git#97 (comment)

I'm willing to add this to kaniko, but I'm not sure how the API should look like.

We already have the possibility to add #refs/heads/x or #refs/tags/x to the URL, adding more options will make it too hard to read IMHO. I was thinking maybe extending it via environment variables or extra flags?

e.g.:

--git-branch
--git-single-branch
--git-recurse-submodules

and so on...

any thoughts?

cc/ @tejal29