If the user double clicks a branch in the checkout dialog then they
probably want to start the checkout process on that branch. I found
myself doing this without realizing it, and of course it did nothing
as there was no action bound to the listbox's Double-Button-1 event
handler. Since I did it without thinking, others will probably also
try, and expect the same behavior.
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
827c71199d