bug#36828: 27.0.50; Uninstalled emacs shows installed documentation

[Óscar Fuentes]

Eli Zaretskii <eliz@gnu.org> writes:

>> Right now I must leave so a quick question: what about beginning with
>> setting data-directory to the source tree in init_callproc_1 when we are
>> running from a non-installed Emacs? (Assuming that we can detect that
>> condition)
>
> We currently detect that by the condition that doesn't work in your
> case:
>
>       if (!NILP (Fequal (srcdir, Vinvocation_directory))
>
> If we solve that problem, we can solve your problem as side effect,
> right?

Yes, I checked that forcing that `if' to true works for NEWS, but I
wonder why we assign Vdata_directory on init_callproc_1 to the installed
Emacs directory ("/usr/local/share/emacs/27.0.50/etc/" on this case)
when we are running a non-installed Emacs. Having Vdata_directory around
pointing to the "wrong" directory looks like a potential problem. And
IMO it is also undesirable to assign it on two different functions, if
we can avoid that.

BTW, fixing the `if' mentioned above also causes C-h r, C-h t and
probably others to use the non-installed docs. Buth C-h i still shows
the directory of info files of the installed version. I guess that
without a `dir' file on the non-installed doc directory we can't solve
this, right?