Gitlab hostname only support.

[Bene81]

Closes #698 .

This merge request offers support for addressing git hosts by hostname only.

The overall idea of this implementation is: if a host uri does not contain any dots it has to be a host in the local network.
If thats the case the resulting credential scope is returned.

Otherwise the old scope determination algorithm applies.
UnitTest has been adapted. I am open for discussions or improvement suggestions.

[ldennington]

Thank you for opening this PR! 🎉 I've added a few suggestions for cleanup, but looks good overall.

[Bene81]

Thanks for your suggestions. I have reviewed and applied them.
Just for my personal understanding: why is it guarenteed that the URL hostname/domain name is either null or whitespace but never string.Empty?

[mjcheetham]

why is it guarenteed that the URL hostname/domain name is either null or whitespace but never string.Empty?

The string.IsNullOrWhiteSpace method also checks for the empty string, and is therefore a superset of the tests used in string.IsNullOrEmpty. C# documentation

Value	string.IsNullOrEmpty	string.IsNullOrWhiteSpace
"foo"	false	false
null	true	true
"" string.Empty	true	true
" "	false	true

I.e, the empty string is also considered whitespace.

[Bene81]

Thanks for hinting. Sorry, should have figured that out myself.