Ticket #3237: fish subshell pwd passing is broken.

Use $PWD variable instead of of calling pwd (which can be a function)
since it is read-only and not manipulated.

Signed-off-by: Andrew Borodin <aborodin@vmail.ru>
Merge branch '3237_fish_pwd'

* 3237_fish_pwd:
  Ticket #3237: fish subshell pwd passing is broken.