Enhance fetch subcommand with -f and multiple groups

[sirnewton01]

The Go 1.11 "go get" with modules is using the fetch command to grab the latest packs from the origin repository. In particular, it needs the "-f" flag and the ability to specify multiple groups like git fetch -f origin refs/heads/_:refs/heads/_ refs/tags/_:refs/tags/

[driusan]

-f looks pretty trivial.. I think that might already be our default behaviour

[driusan]

I've almost got this working, I just need to sort out the dst part

[sirnewton01]

I didn't come across this in my later modules testing. Should we un-tag this from the go_get_complete milestone?

[driusan]

You didn't come across it because of #207, but we still don't support the flag properly