Allow usernames in git resolver

[danharper]

Summary

The Git resolver did not understand usernames in URLs, e.g. git+ssh://[email protected]/... due to it treating any pattern containing @ as being "un-exploded". See #513.

For me it was falling through, and calling the npm resolver instead. The package wasn't published on the registry, so it was erroring there. For others, it would error due to version mismatches if it was on the registry.

Instead, it now checks for @PROTOCOL:, e.g.

// good
git+https://[email protected]/radweb/eslint-config-radweb.git

// bad
eslint-config-radweb@git+https://[email protected]/radweb/eslint-config-radweb.git
                    ^^^^^^^^^^^

Test plan

Added test, they pass.

Btw I've noticed https://github.com/npm-ml/ocaml.git#npm-4.02.3 times out a lot.

[danharper]

I've had chance to look into this more, and found what I think is a more elegant solution. I've opened another PR for that version here: #934.