v0.1.0-beta6

Added

• Add 'stack edit' command to edit an entire stack, similarly to 'downstack edit'.
• Add 'branch split' command to split an existing branch with multiple commits into one or more new branches.

Changed

• upstack restack: Rename --no-base to --skip-start.
• upstack restack: Target branch name is now a --branch flag.
• downstack submit: Optional positional branch argument is now --branch flag.
• downstack edit: Optional positional branch argument is now a --branch flag.
• branch fold: The optional branch name argument is now a flag.
• branch restack: The optional positional argument is now a --branch flag.
• branch submit: Optional branch positional argument is now the --branch flag.

Fixed

• branch submit: If there's a PR template but no commit body, don't add extraneous newlines at the start of the default PR description.
• upstack restack: Fix --no-base ignored when there's only one branch.
• commit {create, amend}: Fix unintended restacking of current branch when there's only one branch in the stack.
• branch onto: Move the upstack of the target branch before the brach itself. This makes the operation better able to recover from conflicts.