27.0.91; default-directory launched via Dock MacOS

[Tak Kunihiro]

I want to launch emacs via Dock or Spotlight on MacOS.

>From scratch buffer on emacs 26.3, C-x C-f prompts home directory
"~/".  However, from scratch buffer on emacs 27.0.91, C-x C-f prompts
root directory "/", which is inconvenient.

When emacs 27.0.91 is started in home directory, C-x C-f prompts
"~/", as expected.

I think that C-x C-f should prompt home directory "~/" instead of root
directory "/" when emacs is launched via Dock or Spotlight.  Since
that worked good until emacs 26.3, something was changed on emacs 27.

Can you store the behavior back?  I show the recipe below to reproduce
the problem.

 $ cd; mv .emacs.d dot.emacs.d
 click emacs 27.0.91 on Dock
 C-x b *scratch*
 C-x C-f ; => Find file: /
 M-x kill-emacs

 $ ./Downloads/emacs-27.0.91/nextstep/Emacs.app/Contents/MacOS/Emacs &
 C-x b *scratch*
 C-x C-f ; => Find file: ~/
 M-x kill-emacs

 click emacs 26.3 on Dock
 C-x b *scratch*
 C-x C-f ;=> Find file: ~/