Repository name preview

[0x5c]

This is a request for a preview of the repository name when creating a repo, like this screenshot, from github.

It could be implemented as a bubble, seen when illegal characters are present in the name box (like above^), or under the box, whether or not the name is invalid.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs during the next 2 weeks. Thank you for your contributions.

[0x5c]

Bump, this is still something that would be nice to get

[wxiaoguang]

The behavior should have been improved by "Fix some migration and repo name problems (#33986)"