Squashed 'third_party/git/' content from commit cb71568594

git-subtree-dir: third_party/git
git-subtree-split: cb715685942260375e1eb8153b0768a376e4ece7

1 files changed, 104 insertions, 0 deletions

diff --git a/perl/Git/LoadCPAN.pm b/perl/Git/LoadCPAN.pm
new file mode 100644
index 000000000000..e5585e75e809
--- /dev/null
+++ b/perl/Git/LoadCPAN.pm
@@ -0,0 +1,104 @@
+package Git::LoadCPAN;
+use 5.008;
+use strict;
+use warnings;
+
+=head1 NAME
+
+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<FromCPAN::Module::Name> shipped with Git itself.
+
+Usually distributors will not ship with Git's Git::FromCPAN tree at
+all via the C<NO_PERL_CPAN_FALLBACKS> option, preferring to use their
+own packaging of CPAN modules instead.
+
+This module is only intended to be used for code shipping in the
+C<git.git> repository. Use it for anything else at your peril!
+
+=cut
+
+# NO_PERL_CPAN_FALLBACKS_STR evades the sed search-replace from the
+# Makefile, and allows for detecting whether the module is loaded from
+# perl/Git as opposed to perl/build/Git, which is useful for one-off
+# testing without having Error.pm et al installed.
+use constant NO_PERL_CPAN_FALLBACKS_STR => '@@' . 'NO_PERL_CPAN_FALLBACKS' . '@@';
+use constant NO_PERL_CPAN_FALLBACKS => (
+	q[@@NO_PERL_CPAN_FALLBACKS@@] ne ''
+	and
+	q[@@NO_PERL_CPAN_FALLBACKS@@] ne NO_PERL_CPAN_FALLBACKS_STR
+);
+
+sub import {
+	shift;
+	my $caller = caller;
+	my %args = @_;
+	my $module = exists $args{module} ? delete $args{module} : die "BUG: Expected 'module' parameter!";
+	my $import = exists $args{import} ? delete $args{import} : die "BUG: Expected 'import' parameter!";
+	die "BUG: Too many arguments!" if keys %args;
+
+	# Foo::Bar to Foo/Bar.pm
+	my $package_pm = $module;
+	$package_pm =~ s[::][/]g;
+	$package_pm .= '.pm';
+
+	eval {
+		require $package_pm;
+		1;
+	} or do {
+		my $error = $@ || "Zombie Error";
+
+		if (NO_PERL_CPAN_FALLBACKS) {
+			chomp(my $error = sprintf <<'THEY_PROMISED', $module);
+BUG: The '%s' module is not here, but NO_PERL_CPAN_FALLBACKS was set!
+
+Git needs this Perl module from the CPAN, and will by default ship
+with a copy of it. This Git was built with NO_PERL_CPAN_FALLBACKS,
+meaning that whoever built it promised to provide this module.
+
+You're seeing this error because they broke that promise, and we can't
+load our fallback version, since we were asked not to install it.
+
+If you're seeing this error and didn't package Git yourself the
+package you're using is broken, or your system is broken. This error
+won't appear if Git is built without NO_PERL_CPAN_FALLBACKS (instead
+we'll use our fallback version of the module).
+THEY_PROMISED
+			die $error;
+		}
+
+		my $Git_LoadCPAN_pm_path = $INC{"Git/LoadCPAN.pm"} || die "BUG: Should have our own path from %INC!";
+
+		require File::Basename;
+		my $Git_LoadCPAN_pm_root = File::Basename::dirname($Git_LoadCPAN_pm_path) || die "BUG: Can't figure out lib/Git dirname from '$Git_LoadCPAN_pm_path'!";
+
+		require File::Spec;
+		my $Git_pm_FromCPAN_root = File::Spec->catdir($Git_LoadCPAN_pm_root, '..', 'FromCPAN');
+		die "BUG: '$Git_pm_FromCPAN_root' should be a directory!" unless -d $Git_pm_FromCPAN_root;
+
+		local @INC = ($Git_pm_FromCPAN_root, @INC);
+		require $package_pm;
+	};
+
+	if ($import) {
+		no strict 'refs';
+		*{"${caller}::import"} = sub {
+			shift;
+			use strict 'refs';
+			unshift @_, $module;
+			goto &{"${module}::import"};
+		};
+		use strict 'refs';
+	}
+}
+
+1;