- Firstly -- add a bunch of unit tests for `update_scm_url`, because it
previously had none and desperately needed them.
- Secondly -- fix#12992 by adding back in IPv6 address brackets if they
existed in the first place when the function was called.
- Thirdly -- fix a related case where we disallowed IPv6 in URLs that
did not include the scheme.
Signed-off-by: Rick Elrod <rick@elrod.me>