prefer Document::set_selection to inserting selections directly (#2411)

Inserting these with the `HashMap::insert` method evades the call
to `Selection::ensure_invariants`. The effect is that the scratch
buffer (or other buffers opened through these code-paths) can start
with a selection at (0, 0), when a file with equivalent contents ("\n")
would start with (0, 1).

I.e.:

    hx

and

    touch f
    hx f

start with different selections even though they have an equivalent
Rope. With this change they both start with (0, 1).

0 files changed, 0 insertions, 0 deletions