Cannot import certain valid repository URLs

[jxxe]

https://github.com/jxxe/yes.period does not work
https://github.com/jxxe/noperiod does work
https://github.com/jxxe/under_score does work

[jxxe]

It also does not allow https://github.com/jxxe/trailing-slash/ and provides an unhelpful error message:

Please enter at least one GitHub repository.