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

[Todd Zullinger <tmz@pobox.com>]

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

-- 
Todd
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Man has made use of his intelligence, he invented stupidity.
    -- Remy De Gourmant