How do cross-project references work? #137

If I'm understanding correctly, references across issues in the same project will have their URLs updated during migration to match the new issue number and repo. So, two issues linked to each other will still be referencing each other after migration.

Q1: Do I have that ☝️ correct?

Q2: And does this also work across projects when multiple projects are named in the projects-map collection?

Q3: Do all projects have to be migrated in one go in order for cross-project refs to work? (I'm thinking rate limits concerns as described in #138 (comment) may otherwise lead a team to migrate just a few projects at a time.)