bug#36828: 27.0.50; Uninstalled emacs shows installed documentation

[Eli Zaretskii <eliz@gnu.org>]

Ping!  Could we please make some progress in this matter?  Can you
please answer my questions below?  TIA

> Date: Tue, 30 Jul 2019 18:08:31 +0300
> From: Eli Zaretskii <eliz@gnu.org>
> Cc: 36828@debbugs.gnu.org, stepnem@gmail.com
> 
> > From: Óscar Fuentes <ofv@wanadoo.es>
> > Cc: stepnem@gmail.com,  36828@debbugs.gnu.org
> > Date: Mon, 29 Jul 2019 23:09:09 +0200
> > 
> > >> M-x describe-function shows the docstrings of the Emacs I'm executing,
> > >
> > > How do you know?  What is the value of doc-directory?
> > 
> > /home/oscar/dev/emacs/stable/build/etc/
> > 
> > The installed version is in /usr/local.
> 
> Hmm... then this is not the use case I had in mind, and some other
> factor is at work here.  Your use case is supposed to be handled by
> this fragment from init_callproc:
> 
>   if (data_dir == 0)
>     {
>       Lisp_Object tem, tem1, srcdir;
>       Lisp_Object lispdir = Fcar (decode_env_path (0, PATH_DUMPLOADSEARCH, 0));
> 
>       srcdir = Fexpand_file_name (build_string ("../src/"), lispdir);
> 
>       tem = Fexpand_file_name (build_string ("NEWS"), Vdata_directory);
>       tem1 = Ffile_exists_p (tem);
>       if (!NILP (Fequal (srcdir, Vinvocation_directory)) || NILP (tem1))
> 	{
> 	  Lisp_Object newdir;
> 	  newdir = Fexpand_file_name (build_string ("../etc/"), lispdir);
> 	  tem = Fexpand_file_name (build_string ("NEWS"), newdir);
> 	  tem1 = Ffile_exists_p (tem);
> 	  if (!NILP (tem1))
> 	    Vdata_directory = newdir;
> 	}
>     }
> 
> So somehow the call to Fequal returns nil in your case, when it
> shouldn't.  Please step with a debugger into this code and see why it
> fails to detect that you are invoking Emacs from the source directory.
> My crystal ball says some symlinks are involved.
> 
> > A quick look at info.el hints that data-directory is also used for
> > locating the info file.
> 
> Only for the NS build.
> 
> > The change would amount to determine if we are running from an
> > uninstalled build and, if positive, set data-directory et al. to the
> > values they would have if no installed instance existed.
> 
> That's the code above, but it somehow isn't working in your case.