default repo tweaks #6827
Description
For gh repo clone and gh repo fork, we should set a default base repo now that it's easy for users to change that after the fact.
In both commands, we should pick the parent repository and print a message about it:
# Cloning a fork
$ gh repo clone vilmibm/cli
! cli/cli selected as default repo for querying issues, pull requests, etc.
! To learn more or change this selection, see: gh repo set-default
# Forking
$ gh repo fork cli/cli
# ... interactive flow
! cli/cli selected as default repo for querying issues, pull requests, etc.
! To learn more or change this selection, see: gh repo set-default
If a gh repo clone operation results in a single remote, we don't need to print anything.