The rail's selection lives in Rust as a set of file paths, so it had no
anchor and stayed toggle-only (750c59034 said as much). The rail now keeps
the anchor path and, on Shift, sends every drawn row from it to the clicked
row to a new treeSelectRange, which SELECTS: a folder with its whole
subtree, a track with its own record, so a range only ever adds. In select
mode a Shift or Ctrl click on a row body selects it instead of opening the
folder; a plain click still opens it.
The rail's selection mutations used to be spawned side by side. With ranges
that became a race: a range that finished before the click that set its
anchor would be undone by that late toggle. They now run one at a time in
click order, with select-all, clear and leaving select mode in the same
queue.
cc
vicrodh
b43771cc3e