* We started with a tristate flag where:
- Auto - Maintain current behaviour. This edits if
the wc parent is not a head commit. Else, it will
create a new commit on the parent of the wc in
the direction of movement.
- Always - Always edit
- Never - Never edit, prefer the new+squash workflow.
However, consensus the review thread is that `auto` mode where we try to infer when to
switch to `edit mode`, should be removed. So `ui.movement.edit` is a boolean flag now.
- true: edit mode
- false: new+squash mode
* Also add a `--no-edit` flag as the explicit inverse of `--edit` and
ensure both flags take precedence over the config.
* Update tests that assumed edit mode inference, to specify `--edit` explicitly.
NOTE: #4302 was squashed into this commit, so see that closed PR for review history.
Part of #3947