From our notes in our weekly meeting today:

Option 1 - no staging repo

• clone master of the repo on instance
• arc patch Dwhatever

Option 2 - single staging repo

• keeping the staging repo up to date on instances
• staging repo likely unmanagably large

Option 3 - staging within each repo

• saves space
• easy to checkout any revision you want (without having to use arc)
• clutters the refs/tags/* namespace with one tag for every differential change
  • Hopefully phabricator will eventually move to using an alternate namespace like refs/changes in gerrit. This would avoid the clutter while maintaining the benefits of staging changes within each repo.