Expect an advanced mode where the user can type the branch to be used in Sandbox.

If native integration is available with the git provider (check based on repository URL), replace the text box with a list of available branches.

• Use isomorphic-git’s https://isomorphic-git.org/docs/en/listServerRefs or https://isomorphic-git.org/docs/en/getRemoteInfo to list branches/tags/default branch.
• If these queries succeed, display a selector to choose what ref to clone. Default branch is always pre-selected. It should be possible to filter branch names on this selector by typing part of this name.
• We will only clone the specific branch.  
• If the queries fail, it means it’s not a Git repository, so other importing options should be attempted.