Re: [PATCH 3/8] perl: generalize the Git::LoadCPAN facility

> Hi Ævar,
>
> Ævar Arnfjörð Bjarmason wrote:
>> +Git::LoadCPAN - Wrapper for loading modules from the CPAN (OS) or Git's own copy
>> +
>> +=head1 DESCRIPTION
>> +
>> +The Perl code in Git depends on some modules from the CPAN, but we
>> +don't want to make those a hard requirement for anyone building from
>> +source.
>> +
>> +Therefore the L<Git::LoadCPAN> namespace shipped with Git contains
>> +wrapper modules like C<Git::LoadCPAN::Module::Name> that will first
>> +attempt to load C<Module::Name> from the OS, and if that doesn't work
>> +will fall back on C<Git::FromCPAN::Module::Name> shipped with Git
>> +itself.
>> +
>> +Usually OS's will not ship with Git's Git::FromCPAN tree at all,
>> +preferring to use their own packaging of CPAN modules instead.
>
> This is something I wondered about.  What's the recommended
> method to ensure git packaged for an OS/distribution doesn't
> ever use the fallbacks?  Remove $perllibdir/Git/FromCPAN
> after make install?
>
> If so, would it be useful to add a Makefile knob to not
> install the FromCPAN bits, which may be generally useful to
> packagers?
>
> Something like the following, perhaps?
>
> (I'd feel bad suggesting this without a patch, after all the
> work you've already done to simplify and improve the perl
> bits.)
>
> ---- 8< ----
> From: Todd Zullinger <tmz@pobox.com>
> Date: Wed, 14 Feb 2018 23:00:30 -0500
> Subject: [PATCH] Makefile: add NO_PERL_CPAN to disable fallback module install
>
> As noted in perl/Git/LoadCPAN.pm, operating system packages often don't
> want to ship Git::FromCPAN tree at all, preferring to use their own
> packaging of CPAN modules instead.  Allow such packagers to set
> NO_PERL_CPAN to easily avoid installing these fallback perl CPAN
> modules.
>
> Signed-off-by: Todd Zullinger <tmz@pobox.com>
> ---
>  Makefile | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/Makefile b/Makefile
> index 5bcd83ddf3..c4e035e5bf 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -296,6 +296,9 @@ all::
>  #
>  # Define NO_PERL if you do not want Perl scripts or libraries at all.
>  #
> +# Define NO_PERL_CPAN if you do not want to install fallbacks for perl CPAN
> +# modules.
> +#
>  # Define PYTHON_PATH to the path of your Python binary (often /usr/bin/python
>  # but /usr/bin/python2.7 on some platforms).
>  #
> @@ -2572,6 +2575,7 @@ ifndef NO_GETTEXT
>  endif
>  ifndef NO_PERL
>  	$(INSTALL) -d -m 755 '$(DESTDIR_SQ)$(perllibdir_SQ)'
> +	test -z "$(NO_PERL_CPAN)" || rm -rf perl/build/lib/Git/FromCPAN
>  	(cd perl/build/lib && $(TAR) cf - .) | \
>  	(cd '$(DESTDIR_SQ)$(perllibdir_SQ)' && umask 022 && $(TAR) xof -)
>  	$(MAKE) -C gitweb install
> --
> 2.16.1
>
> I don't particularly like NO_PERL_CPAN, but I'm confident
> someone else will suggest an obviously better name.
>
> I thought about moving the 'rm -rf Git/FromCPAN' after the
> tar/untar, to keep the files in place for the tests.  No
> tests seem to rely on those local files, so I stuck with
> removing them before.  That diff was:
>
> --- a/Makefile
> +++ b/Makefile
> @@ -2574,6 +2574,7 @@
>  	$(INSTALL) -d -m 755 '$(DESTDIR_SQ)$(perllibdir_SQ)'
>  	(cd perl/build/lib && $(TAR) cf - .) | \
>  	(cd '$(DESTDIR_SQ)$(perllibdir_SQ)' && umask 022 && $(TAR) xof -)
> +	test -n "$(NO_PERL_CPAN)" && rm -rf '$(DESTDIR_SQ)$(perllibdir_SQ)'/Git/FromCPAN
>  	$(MAKE) -C gitweb install
>  endif
>  ifndef NO_TCLTK