This is the flow that a user can start from the Branch | Rebase current branch... menu item which lets the user:

• select the base branch to merge the current branch onto
• see at a glance how many commits will be rebased
• view the progress of the rebase
• be interrupted by the rebase if it encounters conflicts (ask user to resolve rebase conflicts before continuing #6548 is related to this step)
• see some sort of success indicator when it completes

The mocks for this can be seen in this comment: #5953 (comment)

TODO:

• flesh out the checklist of tasks