The working-directory capture (used to restart a local shell where it
left off) ran /usr/sbin/lsof inside write(), so each Enter in a macOS
local tab waited for a subprocess. On macOS the lookup now runs on a
background thread, triggered by the shell's next output after a line is
entered, so it sees the directory after the command; a failed lookup
keeps the last known directory. Linux keeps the cheap /proc readlink
(F10). Not exercised on macOS in this environment.
Andy Dixon
c6ee9a8f36