v0.1.0-beta1

Added

• Add gs rebase continue (alias gs rbc) and gs rebase abort (alias gs rba) to continue git-spice operations interrupted by rebase conflicts.
• Add 'upstack onto' command to move a branch and its upstack onto a new base. This was previously the behavior of 'branch onto'.

Changed

• branch {edit, onto}: Support continuing the operation after resolving conflicts with gs rebase continue.
• {branch, upstack, stack} restack: Support continuing the operation after resolving conflicts with gs rebase continue.
• (Breaking) branch onto: Extract only the commits of the target branch onto the new base. The upstack will be rebased to point to its base. Use 'upstack onto' to graft the entire upstack onto the new base.
• (Breaking) branch delete: Remove commits of the deleted branch from the stack. If you want to keep them around, untrack the branch instead.
• branch delete: In the selection prompt for deleting a branch, default to the current branch.

Fixed

• Reduce boilerplate in rebase error messages.
• branch delete: Don't report an empty hash for untracked branches.