feat: support specifying branch for cloning

[caarlos0]

this allows to specify a reference to clone in the same way npm allows: appending #reference to the URL, eg: git://github.com/GoogleContainerTools#refs/tags/v0.10.0

I'm not sure this is a good approach, but was the one I could think of without needing to change much.

[bryanhuntesl]

@caarlos0 - could you push a no-op commit to get the checks completed - they're blocking on "kokoro Expected — Waiting for status to be reported "

[bryanhuntesl]

@caarlos0 - and, sorry to bother you again - do you think it's possible to get the checksum argument into the URL?

I'd be willing to try implementing if you/they were interested (erlang dev here - but I'll try).

I've been trying to get some feedback on https://groups.google.com/forum/#!topic/kaniko-users/G4TieNB8YaM

[caarlos0]

@caarlos0 - and, sorry to bother you again - do you think it's possible to get the checksum argument into the URL?

AFAIK no, only branches and tags :/

Would need to do a full clone and then git checkout the given reference for it to work...

[caarlos0]

@caarlos0 - could you push a no-op commit to get the checks completed - they're blocking on "kokoro Expected — Waiting for status to be reported "

yeah seems like it refuses to run for some reason

[caarlos0]

cc/ @priyawadhwa

[priyawadhwa]

lgtm!

[bryanhuntesl]

Thanks @priyawadhwa !

[caarlos0]

thanks!