reopen 2631
retitle 2631 get-free-disk-space when home dir also doesn't exist
tags 2631 +patch
thanks

If both default-directory and home directory both don't exist
get-free-disk-space still gets an error

    (progn
      (setq default-directory "/no/such/dir")
      (setenv "HOME" "/another/no/such/dir")
      (get-free-disk-space "/"))
    => (file-error "Setting current directory" "no such file or directory" "/another/no/such/dir/")

Although plenty of things probably depend on a home dir I don't think
get-free-disk-space needs to be one of them.

Change below is like what's also in the following funcs, I believe for
the same purpose, ie. just to make sure call-process will be happy, when
the program run doesn't care about the current directory.

    Man-init-defvars,
    mail-source-movemail
    message-send-mail-with-sendmail
    sendmail-send-it
    gamegrid-add-score-with-update-game-score-1