Pressing the left button on the current selection now starts a drag
that moves the selected commits, both in the normal commits view and
for todos during an interactive rebase. A press anywhere else falls
through to the usual click handling, so dragging from an unselected
line still creates a range selection, and releasing without having
moved collapses the selection to the pressed commit like a plain click
would.
While dragging, the insertion point follows the pointer: rows below
the dragged block insert after the pointed-at commit, rows above it
insert before it, and during a rebase the destination is limited to
the contiguous block of movable todos around the selection. gocui
moves the view cursor along with the pointer, so each drag event moves
it back to keep the original selection highlighted.
The move happens on release. The model may have been refreshed during
the drag, so the dragged commits are located again by their identity
(hash, subject, todo action); if they no longer form a unique
contiguous block, the drop is ignored rather than guessing.
