Feature request: `gem sources --add` should write new source without hitting the URL first.

I'm having a problem or would like to suggest a feature.

My current problem is gem sources requiring authentication cannot be added using gem sources --add without including the user:pass authentication components in the URL. This writes private authentication information to ~/.gemrc.

This issue is related to:

• Network problems
• Installing a library
• Publishing a library
• The command line gem
• Other

Here are my current environment details:

$ gem env version
2.2.2

I will abide by the code of conduct.

I much prefer to keep the authentication information outside of .gemrc by using bundle config (or more specifically, the BUNDLER_* env vars). Which means the gem source needs to be added to .gemrc without the authentication components. However, doing gem sources --add <source_url_without_auth> fails because the unauthenticated URL returns a 401. I propose that gem sources --add either:

1. add a flag to disable the preflight check
2. write the source to .gemrc first and then hit the url, emitting an error message as appropriate and returning the proper error code.

My vote is for option 2.

Start at the implementation of the gem sources --add command and trace its .gemrc write and URL preflight behavior. Compare the proposed alternatives, then verify that an unauthenticated source can be written without exposing credentials while the command still reports URL errors and returns the proper status.