Modular object-orientied buildsystem implementation (try 2).

Major changess:

* Dh_Buildsystem_Option dropped and Dh_Buildsystem_Chdir functionality
  partitially merged into Dh_Buildsystem_Basic. Dh_Buildsystem_Bases.pm
  renamed to Dh_Buildsystem_Basic.pm to match classname.
* *_impl() ditched completely. Previous {configure,build,test,install,clean}_impl()
  renamed to just configure(), build(), test(), install(), clean() instead.
  Added pre_action($action) and post_action($action) hooks instead which are called
  by Dh_Buildsystems::buildsystems_do().
* Builddir is handled via mkdir_builddir(), doit_in_buildddir(), clean_builddir()
  methods which buildsystems should call directly. Removed get_top* method, added
  get_rel2builddir_path().
* is_buildable() method renamed to is_auto_buildable() to reflect its
  purpose more.
* ::perl_makefile renamed to ::perl_makemaker and which is based on ::makefile
  now. MakeMaker hack moved from ::makefile to ::perl_makemaker where it belongs
  (thanks for the tip).
* Dh_Buildsystems refactored into a simple perl module rather than OO class and
  simplified a bit.
* @BUILDSYSTEMS and is_auto_buildable() modified to 100% match historical order.

TODO: user documentation (e.g. DH_AUTO_BUILDDIRECTORY and DH_AUTO_BUILDSYSTEM
environment variables and common dh_auto_* options (--buildsystem and --builddirectory)).

Current plugin inheritance hierarchy is like this:

    Buildsystem::perl_build -> Dh_Buildsystem_Basic  <- Buildsystem::python_distutils
                                      ^
                                      |
                              Buildsystem::makefile  <- Buildsystem::perl_makemaker
                              ^       ^           ^
                             /        |             \
       Buildsystem::autotools  Buildsystem::cmake   Buildsystem::python_distutils

Signed-off-by: Modestas Vainius <modestas@vainius.eu>

15 files changed, 568 insertions, 656 deletions

diff --git a/Debian/Debhelper/Buildsystem/autotools.pm b/Debian/Debhelper/Buildsystem/autotools.pm
index 945ca408..1ebc9384 100644
--- a/Debian/Debhelper/Buildsystem/autotools.pm
+++ b/Debian/Debhelper/Buildsystem/autotools.pm
@@ -15,17 +15,18 @@ sub DESCRIPTION {
 	"support for building GNU Autotools based packages"
 }
 
-sub is_buildable {
+sub is_auto_buildable {
 	my $self=shift;
-	my ($action) = @_;
+	my $action=shift;
+
+	# Handle configure; the rest - next class
 	if ($action eq "configure") {
 		return -x "configure";
-	} else {
-		return $self->SUPER::is_buildable(@_);
 	}
+	return 0;
 }
 
-sub configure_impl {
+sub configure {
 	my $self=shift;
 
 	# Standard set of options for configure.
@@ -37,17 +38,7 @@ sub configure_impl {
 	push @opts, "--infodir=\${prefix}/share/info";
 	push @opts, "--sysconfdir=/etc";
 	push @opts, "--localstatedir=/var";
-	# XXX JEH this is where the sheer evil of Dh_Buildsystem_Chdir
-	# becomes evident. Why is exec_in_topdir needed here?
-	# Because:
-	# - The parent class happens to be derived from Dh_Buildsystem_Chdir.
-	# - sourcepage() happens to, like many other parts of debhelper's
-	#   library, assume it's being run in the top of the source tree,
-	#   and fails if it's not.
-	# Having to worry about interactions like that for every line of
-	# every derived method is simply not acceptable.
-	# Dh_Buildsystem_Chdir must die! -- JEH
-	push @opts, "--libexecdir=\${prefix}/lib/" . $self->exec_in_topdir(\&sourcepackage);
+	push @opts, "--libexecdir=\${prefix}/lib/" . sourcepackage();
 	push @opts, "--disable-maintainer-mode";
 	push @opts, "--disable-dependency-tracking";
 	# Provide --host only if different from --build, as recommended in
@@ -62,7 +53,9 @@ sub configure_impl {
 	# but does not need to in the is_buildable method is not clear,
 	# unless one is familiar with the implementation of its parent
 	# class. I think that speaks to a bad design..
-	doit($self->get_toppath("configure"), @opts, @_);
+	# XXX MDX It should be more explicit now.
+	$self->mkdir_builddir();
+	$self->doit_in_builddir($self->get_rel2builddir_path("configure"), @opts, @_);
 }
 
 1;
diff --git a/Debian/Debhelper/Buildsystem/cmake.pm b/Debian/Debhelper/Buildsystem/cmake.pm
index 00f6be4d..026004a0 100644
--- a/Debian/Debhelper/Buildsystem/cmake.pm
+++ b/Debian/Debhelper/Buildsystem/cmake.pm
@@ -10,45 +10,43 @@ use strict;
 use Debian::Debhelper::Dh_Lib;
 use base 'Debian::Debhelper::Buildsystem::makefile';
 
-sub _add_cmake_flag {
-	my ($self, $name, $val) = @_;
-	push @{$self->{cmake_flags}}, "-D$name=$val";
-}
-
 sub DESCRIPTION {
 	"support for building CMake based packages (outside-source tree only)"
 }
 
-sub is_buildable {
-	return -e "CMakeLists.txt";
+sub is_auto_buildable {
+	my $self=shift;
+	my ($action)=@_;
+	my $ret = -e "CMakeLists.txt";
+	$ret &&= $self->SUPER::is_auto_buildable(@_) if $action ne "configure";
+	return $ret;
 }
 
 sub new {
 	my $cls=shift;
 	my $self=$cls->SUPER::new(@_);
-	# Enfore outside-source tree builds.
+	# Enforce outside-source tree builds.
 	$self->enforce_outside_source_building();
-	$self->{cmake_flags} = [];
 	return $self;
 }
 
-sub configure_impl {
+sub configure {
 	my $self=shift;
+	my @flags;
 
 	# Standard set of cmake flags
-	$self->_add_cmake_flag("CMAKE_INSTALL_PREFIX", "/usr");
-	$self->_add_cmake_flag("CMAKE_C_FLAGS", $ENV{CFLAGS}) if (exists $ENV{CFLAGS});
-	$self->_add_cmake_flag("CMAKE_CXX_FLAGS", $ENV{CXXFLAGS}) if (exists $ENV{CXXFLAGS});
-	$self->_add_cmake_flag("CMAKE_SKIP_RPATH", "ON");
-	$self->_add_cmake_flag("CMAKE_VERBOSE_MAKEFILE", "ON");
-	# TODO: LDFLAGS
-	# XXX JEH why are we using a method and an object
-	# field to build up a simple one-time-use list?
-	# 	my @flags;
-	# 	push @flags, ... if $foo
-
-	# XXX JEH again a non-sequitor get_topdir. 
-	doit("cmake", $self->get_topdir(), @{$self->{cmake_flags}}, @_);
+	push @flags, "-DCMAKE_INSTALL_PREFIX=/usr";
+	push @flags, "-DCMAKE_C_FLAGS=$ENV{CFLAGS}" if (exists $ENV{CFLAGS});
+	push @flags, "-DCMAKE_CXX_FLAGS=$ENV{CXXFLAGS}" if (exists $ENV{CXXFLAGS});
+	push @flags, "-DCMAKE_LD_FLAGS=$ENV{LDFLAGS}" if (exists $ENV{LDFLAGS});
+	push @flags, "-DCMAKE_SKIP_RPATH=ON";
+	push @flags, "-DCMAKE_VERBOSE_MAKEFILE=ON";
+
+	# XXX JEH again a non-sequitor get_topdir.
+	# XXX MDX I cannot avoid it as I need to pass the path to the sourcedir
+	# to cmake which is relative to the builddir.
+	$self->mkdir_builddir();
+	$self->doit_in_builddir("cmake", $self->get_rel2builddir_path(), @flags);
 }
 
 1;
diff --git a/Debian/Debhelper/Buildsystem/makefile.pm b/Debian/Debhelper/Buildsystem/makefile.pm
index cbd9e3c3..7ffb048e 100644
--- a/Debian/Debhelper/Buildsystem/makefile.pm
+++ b/Debian/Debhelper/Buildsystem/makefile.pm
@@ -8,30 +8,41 @@ package Debian::Debhelper::Buildsystem::makefile;
 
 use strict;
 use Debian::Debhelper::Dh_Lib;
-use Debian::Debhelper::Dh_Buildsystem_Bases;
-use base 'Debian::Debhelper::Dh_Buildsystem_Chdir';
+use base 'Debian::Debhelper::Dh_Buildsystem_Basic';
+
+# XXX JEH setting this env var is dodgy,
+# probably better to test if it exists with a default value.
+# (Factor out to helper function?)
+# XXX MDX Done. See new().
+
+sub get_makecmd_C {
+	my $self=shift;
+	if ($self->get_builddir()) {
+		return $self->{makecmd} . " -C " . $self->get_builddir();
+	}
+	return $self->{makecmd};
+}
 
 # XXX JEH I *like* this. Yay for factoring out ugly ugly stuff!
-sub _exists_make_target {
-	my ($cls, $target) = @_;
+# XXX MDX TODO: this could use dh debian/rules parser.
+sub exists_make_target {
+	my ($self, $target) = @_;
+	my $makecmd=$self->get_makecmd_C();
+
 	# Use make -n to check to see if the target would do
 	# anything. There's no good way to test if a target exists.
-	my $ret=`$ENV{MAKE} -s -n $target 2>/dev/null`;
+	my $ret=`$makecmd -s -n $target 2>/dev/null`;
 	chomp $ret;
 	return length($ret);
 }
 
-sub _make_first_existing_target {
-	my $cls = shift;
-	my $targets = shift;
+sub make_first_existing_target {
+	my $self=shift;
+	my $targets=shift;
 
-	# XXX JEH setting this env var is dodgy,
-	# probably better to test if it exists with a default value.
-	# (Factor out to helper function?)
-	$ENV{MAKE}="make" unless exists $ENV{MAKE};
 	foreach my $target (@$targets) {
-		if ($cls->_exists_make_target($target)) {
-			doit($ENV{MAKE}, $target, @_);
+		if ($self->exists_make_target($target)) {
+			$self->doit_in_builddir($self->{makecmd}, $target, @_);
 			return $target;
 		}
 	}
@@ -42,56 +53,49 @@ sub DESCRIPTION {
 	"support for building Makefile based packages (make && make install)"
 }
 
-sub is_buildable {
+sub new {
+	my $cls=shift;
+	my $self=$cls->SUPER::new(@_);
+	$self->{makecmd} = (exists $ENV{MAKE}) ? $ENV{MAKE} : "make";
+	return $self;
+}
+
+sub is_auto_buildable {
 	my $self=shift;
 	my ($action) = @_;
+
+	# Handles build, test, install, clean; configure - next class
 	if (grep /^\Q$action\E$/, qw{build test install clean}) {
-		# XXX JEH why does get_buildpath need to be used 
-		# here? is_buildable is run at the top of the source
-		# directory, so -e 'Makefile' should be the same
+		# This is always called in the source directory, but generally
+		# Makefiles are created (or live) in the the build directory.
 		return -e $self->get_buildpath("Makefile") ||
 		       -e $self->get_buildpath("makefile") ||
 		       -e $self->get_buildpath("GNUmakefile");
-	} else {
-		# XXX JEH why return 1 here?
-		return 1;
 	}
+	return 0;
 }
 
-sub build_impl {
+sub build {
 	my $self=shift;
-	doit(exists $ENV{MAKE} ? $ENV{MAKE} : "make", @_);
+	$self->doit_in_builddir($self->{makecmd}, @_);
 }
 
-sub test_impl {
+sub test {
 	my $self=shift;
-	$self->_make_first_existing_target(['test', 'check'], @_);
+	$self->make_first_existing_target(['test', 'check'], @_);
 }
 
-sub install_impl {
+sub install {
 	my $self=shift;
 	my $destdir=shift;
-
-	# XXX JEH again with the setting the env var, see above..
-	$ENV{MAKE}="make" unless exists $ENV{MAKE};
-	my @params="DESTDIR=$destdir";
-
-	# Special case for MakeMaker generated Makefiles.
-	# XXX JEH This is a really unfortunate breaking of the
-	# encapsulation of the perl_makefile module. Perhaps it would be
-	# better for that module to contain some hack that injects that
-	# test into this one?
-	if (-e "Makefile" &&
-	    system('grep -q "generated automatically by MakeMaker" Makefile') == 0) {
-		push @params, "PREFIX=/usr";
-	}
-
-	$self->_make_first_existing_target(['install'], @params, @_);
+	$self->make_first_existing_target(['install'], "DESTDIR=$destdir", @_);
 }
 
-sub clean_impl {
+sub clean {
 	my $self=shift;
-	$self->_make_first_existing_target(['distclean', 'realclean', 'clean'], @_);
+	if (!$self->clean_builddir()) {
+		$self->make_first_existing_target(['distclean', 'realclean', 'clean'], @_);
+	}
 }
 
 1;
diff --git a/Debian/Debhelper/Buildsystem/perl_build.pm b/Debian/Debhelper/Buildsystem/perl_build.pm
index a43d65da..9be71a27 100644
--- a/Debian/Debhelper/Buildsystem/perl_build.pm
+++ b/Debian/Debhelper/Buildsystem/perl_build.pm
@@ -8,26 +8,27 @@ package Debian::Debhelper::Buildsystem::perl_build;
 
 use strict;
 use Debian::Debhelper::Dh_Lib;
-use Debian::Debhelper::Dh_Buildsystem_Bases;
 use base 'Debian::Debhelper::Dh_Buildsystem_Basic';
 
 sub DESCRIPTION {
 	"support for building Perl Build.PL based packages (in-source only)"
 }
 
-sub is_buildable {
+sub is_auto_buildable {
 	my ($self, $action) = @_;
-	my $ret = (-e "Build.PL");
+
+	# Handles everything
+	my $ret = -e "Build.PL";
 	if ($action ne "configure") {
-		$ret &= (-e "Build");
+		$ret &&= -e "Build";
 	}
 	return $ret;
 }
 
-sub invoke_impl {
+sub do_perl {
 	my $self=shift;
 	$ENV{MODULEBUILDRC} = "/dev/null";
-	return $self->SUPER::invoke_impl(@_);
+	doit("perl", @_);
 }
 
 sub new {
@@ -37,33 +38,31 @@ sub new {
 	return $self;
 }
 
-sub configure_impl {
+sub configure {
 	my $self=shift;
-	# XXX JEH I think the below comment is inherited from elsewhere;
-	# doesn't really make sense now.
-	$ENV{PERL_MM_USE_DEFAULT}=1; # Module::Build can also use this.
-	doit("perl", "Build.PL", "installdirs=vendor", @_);
+	$ENV{PERL_MM_USE_DEFAULT}=1;
+	$self->do_perl("Build.PL", "installdirs=vendor", @_);
 }
 
-sub build_impl {
+sub build {
 	my $self=shift;
-	doit("perl", "Build", @_);
+	$self->do_perl("Build", @_);
 }
 
-sub test_impl {
+sub test {
 	my $self=shift;
-	doit(qw/perl Build test/, @_);
+	$self->do_perl("Build", "test", @_);
 }
 
-sub install_impl {
+sub install {
 	my $self=shift;
 	my $destdir=shift;
-	doit("perl", "Build", "install", "destdir=$destdir", "create_packlist=0", @_);
+	$self->do_perl("Build", "install", "destdir=$destdir", "create_packlist=0", @_);
 }
 
-sub clean_impl {
+sub clean {
 	my $self=shift;
-	doit("perl", "Build", "--allow_mb_mismatch", 1, "distclean", @_);
+	$self->do_perl("Build", "--allow_mb_mismatch", 1, "distclean", @_);
 }
 
 1;
diff --git a/Debian/Debhelper/Buildsystem/perl_makefile.pm b/Debian/Debhelper/Buildsystem/perl_makefile.pm
deleted file mode 100644
index 67a6f441..00000000
--- a/Debian/Debhelper/Buildsystem/perl_makefile.pm
+++ /dev/null
@@ -1,38 +0,0 @@
-# A buildsystem plugin for handling Perl Build based projects.
-#
-# Copyright: © 2008-2009 Joey Hess
-#            © 2008-2009 Modestas Vainius
-# License: GPL-2+
-
-package Debian::Debhelper::Buildsystem::perl_makefile;
-
-use strict;
-use Debian::Debhelper::Dh_Lib;
-use Debian::Debhelper::Dh_Buildsystem_Bases;
-use base 'Debian::Debhelper::Dh_Buildsystem_Basic';
-
-sub DESCRIPTION {
-	"support for building Perl Makefile.PL based packages (in-source only)"
-}
-
-sub is_buildable {
-	my ($self, $action) = @_;
-	return ($action eq "configure")  && (-e "Makefile.PL");
-}
-
-sub new {
-	my $cls=shift;
-	my $self=$cls->SUPER::new(@_);
-	$self->enforce_in_source_building();
-	return $self;
-}
-
-sub configure_impl {
-	my $self=shift;
-	# If set to a true value then MakeMaker's prompt function will
-	# # always return the default without waiting for user input.
-	$ENV{PERL_MM_USE_DEFAULT}=1;
-	doit("perl", "Makefile.PL", "INSTALLDIRS=vendor", @_);
-}
-
-1;
diff --git a/Debian/Debhelper/Buildsystem/perl_makemaker.pm b/Debian/Debhelper/Buildsystem/perl_makemaker.pm
new file mode 100644
index 00000000..15539588
--- /dev/null
+++ b/Debian/Debhelper/Buildsystem/perl_makemaker.pm
@@ -0,0 +1,71 @@
+# A buildsystem plugin for handling Perl MakeMaker based projects.
+#
+# Copyright: © 2008-2009 Joey Hess
+#            © 2008-2009 Modestas Vainius
+# License: GPL-2+
+
+package Debian::Debhelper::Buildsystem::perl_makemaker;
+
+use strict;
+use Debian::Debhelper::Dh_Lib;
+use base 'Debian::Debhelper::Buildsystem::makefile';
+
+sub DESCRIPTION {
+	"support for building Perl MakeMaker based packages (in-source only)"
+}
+
+sub is_auto_buildable {
+	my ($self, $action)=@_;
+
+	# Handles configure, install; the rest - next class
+	if ($action eq "install") {
+		# This hack is needed to keep full 100% compatibility with previous
+		# debhelper versions.
+		if (-e "Makefile" &&
+		    system('grep -q "generated automatically by MakeMaker" Makefile') == 0) {
+			return 1;
+		}
+	}
+	elsif ($action eq "configure") {
+		return -e "Makefile.PL";
+	}
+	else {
+		return 0;
+	}
+}
+
+sub new {
+	my $cls=shift;
+	my $self=$cls->SUPER::new(@_);
+	$self->enforce_in_source_building();
+	return $self;
+}
+
+sub configure {
+	my $self=shift;
+	# If set to a true value then MakeMaker's prompt function will
+	# # always return the default without waiting for user input.
+	$ENV{PERL_MM_USE_DEFAULT}=1;
+	doit("perl", "Makefile.PL", "INSTALLDIRS=vendor", @_);
+}
+
+sub install {
+	my $self=shift;
+	my $destdir=shift;
+	# XXX JEH This is a really unfortunate breaking of the
+	# encapsulation of the perl_makefile module. Perhaps it would be
+	# better for that module to contain some hack that injects that
+	# test into this one?
+	# XXX MDX Solved. perl_makemaker will need come before makefile in
+	# @BUILDSYSTEMS. See also hack in is_auto_buildable().
+	# This is a safety check needed to keep 100% compatibility with
+	# earlier debhelper behaviour. This if is very unlikely to be false.
+	if (-e "Makefile" &&
+	    system('grep -q "generated automatically by MakeMaker" Makefile') == 0) {
+		$self->SUPER::install($destdir, "PREFIX=/usr", @_);
+	} else {
+		$self->SUPER::install($destdir, @_);
+	}
+}
+
+1;
diff --git a/Debian/Debhelper/Buildsystem/python_distutils.pm b/Debian/Debhelper/Buildsystem/python_distutils.pm
index 2e7eacbb..a69b36f4 100644
--- a/Debian/Debhelper/Buildsystem/python_distutils.pm
+++ b/Debian/Debhelper/Buildsystem/python_distutils.pm
@@ -9,54 +9,47 @@ package Debian::Debhelper::Buildsystem::python_distutils;
 
 use strict;
 use Debian::Debhelper::Dh_Lib;
-use Debian::Debhelper::Dh_Buildsystem_Bases;
-use base 'Debian::Debhelper::Dh_Buildsystem_Option';
+use base 'Debian::Debhelper::Dh_Buildsystem_Basic';
 
 sub DESCRIPTION {
 	"support for building Python distutils based packages"
 }
 
-sub is_buildable {
-	return -e "setup.py";
+sub is_auto_buildable {
+	my $self=shift;
+	my $action=shift;
+
+	# Handle build install clean; the rest - next class
+	if (grep(/^\Q$action\E$/, qw{build install clean})) {
+		return -e "setup.py";
+	}
+	return 0;
 }
 
-sub get_builddir_option {
+sub setup_py {
 	my $self=shift;
+	my $act=shift;
+
 	if ($self->get_builddir()) {
-		return "--build-base=". $self->get_builddir();
+		unshift @_, "--build-base=" . $self->get_builddir();
 	}
-	return;
+	doit("python", "setup.py", $act, @_);
 }
 
-# XXX JEH the default for all these methods is to do nothing successfully.
-# So either this, or those default stubs, need to be removed.
-sub configure_impl {
-	# Do nothing
-	1;
-}
-
-sub build_impl {
+sub build {
 	my $self=shift;
-	doit("python", "setup.py", "build", @_);
-}
-
-# XXX JEH see anove comment
-sub test_impl {
-	1;
+	$self->setup_py("build", @_);
 }
 
-sub install_impl {
+sub install {
 	my $self=shift;
 	my $destdir=shift;
-
-	doit("python", "setup.py", "install", 
-	     "--root=$destdir",
-	     "--no-compile", "-O0", @_);
+	$self->setup_py("install", "--root=$destdir", "--no-compile", "-O0", @_);
 }
 
-sub clean_impl {
+sub clean {
 	my $self=shift;
-	doit("python", "setup.py", "clean", "-a", @_);
+	$self->setup_py("clean", "-a", @_);
 	# The setup.py might import files, leading to python creating pyc
 	# files.
 	doit('find', '.', '-name', '*.pyc', '-exec', 'rm', '{}', ';');
diff --git a/Debian/Debhelper/Dh_Buildsystem_Bases.pm b/Debian/Debhelper/Dh_Buildsystem_Bases.pm
deleted file mode 100644
index 24164537..00000000
--- a/Debian/Debhelper/Dh_Buildsystem_Bases.pm
+++ /dev/null
@@ -1,352 +0,0 @@
-# Defines base debhelper buildsystem class interface.
-#
-# Copyright: © 2008-2009 Modestas Vainius
-# License: GPL-2+
-
-# XXX JEH file name does not match package name (Bases vs Basic)
-# That will cause problems when using 'use' to load the module.
-package Debian::Debhelper::Dh_Buildsystem_Basic;
-
-use Cwd;
-use File::Spec;
-use Debian::Debhelper::Dh_Lib;
-
-# Build system name. Defaults to the last component of the package
-# name. Do not override this method unless you know what you are
-# doing.
-# XXX JEH s/package/class/ in above comment for clarity..
-sub NAME {
-	my $self = shift;
-	my $cls = ref($self) || $self;
-	return ($cls =~ m/^.+::([^:]+)$/) ? $1 : "[invalid package name]";
-	# XXX JEH s/package/class/ in above message for clarity..
-	# (maybe dying on this unusual error would be better tho?)
-}
-
-# Description of the build system to be shown to the users.
-sub DESCRIPTION {
-	"basic debhelper build system class";
-}
-
-sub new {
-	my ($cls, $builddir) = @_;
-	# XXX JEH probably would be better to use named parameters here
-	# Also, if the builddir value is not specified, it could use
-	# DEFAULT_BUILD_DIRECTORY here. Which would allow moving that
-	# sub from Dh_Buildsystems to here, since it would no longer need
-	# to be used there.
-	my $self = bless({ builddir => $builddir }, $cls);
-	if (!defined($builddir) || $builddir eq ".") {
-		$self->{builddir} = undef;
-	}
-	return $self;
-}
-
-# This instance method is called to check if the build system is capable
-# to build a source package. Additional argument $action describes which
-# operation the caller is going to perform first (either configure,
-# build, test, install or clean). You must override this method for the
-# build system module to be ever picked up automatically.
-#
-# This method is supposed to be called with source root directory being
-# working directory. Use $self->get_buildpath($path) method to get full
-# path to the files in the build directory.
-sub is_buildable {
-	my $self=shift;
-	my ($action) = @_;
-	return 0;
-}
-
-# Derived class can call this method in its constructor
-# to enforce in-source building even if the user
-# requested otherwise.
-sub enforce_in_source_building {
-	my $self=shift;
-	if ($self->{builddir}) {
-		warning("warning: ".$self->NAME()." buildsystem does not support building outside-source. In-source build enforced.");
-		$self->{builddir} = undef;
-	}
-}
-
-sub get_builddir {
-	my $self=shift;
-	return $self->{builddir};
-}
-
-sub get_buildpath {
-	my ($self, $path) = @_;
-	if ($self->get_builddir()) {
-		return File::Spec->catfile($self->get_builddir(), $path);
-	}
-	else {
-		return File::Spec->catfile('.', $path);
-	}
-}
-
-# XXX JEH this method seems entirely useless.
-# 	$self->invoke_impl('foo', @_);
-# 	$self->foo(@_);
-# The second is easier to both read and write.
-#
-# Turns out that one build system overrides this method,
-# perl_build uses it to set an env vatiable before each method
-# call. But that's unnecessary; it could just set it in its constructor.
-#
-# And there's another version of this method in the derifed class below,
-# which just adds another parameter to the method call. That is used only
-# by the python_distutils build system, to add a --build-base parameter
-# to two calls to python. It could be manually added to those two calls
-# with less fuss.
-sub invoke_impl {
-	my $self=shift;
-	my $method=shift;
-
-	return $self->$method(@_);
-}
-
-# The instance methods below provide support for configuring,
-# building, testing, install and cleaning source packages.
-# These methods are wrappers around respective *_impl() methods
-# which are supposed to do real buildsystem specific work. 
-
-# XXX JEH if invoke_impl is done away with, these can be replaced
-# with the bodies of the foo_impl methods they call. That layer of
-# indirection is not really needed.
-
-sub configure {
-	my $self=shift;
-	return $self->invoke_impl('configure_impl', @_);
-}
-
-sub build {
-	my $self=shift;
-	return $self->invoke_impl('build_impl', @_);
-}
-
-sub test {
-	my $self=shift;
-	return $self->invoke_impl('test_impl', @_);
-}
-
-sub install {
-	my $self=shift;
-	return $self->invoke_impl('install_impl', @_);
-}
-
-sub clean {
-	my $self=shift;
-	return $self->invoke_impl('clean_impl', @_);
-}
-
-# The instance methods below should be overriden by derived classes
-# to implement buildsystem specific actions needed to build the
-# source. Arbitary number of custom action arguments might be passed.
-# Default implementations do nothing.
-
-
-
-sub configure_impl {
-	my $self=shift;
-	1;
-}
-
-sub build_impl {
-	my $self=shift;
-	1;
-}
-
-sub test_impl {
-	my $self=shift;
-	1;
-}
-
-# destdir parameter specifies where to install files.
-# XXX JEH I don't see where this destdir parameter is passed in
-# to a call to $object->install ? In Dh_Buildsystems it does:
-#                 return $buildsystem->$toolname(@_, @{$dh{U_PARAMS}});
-# Which passes a different parameter, to ALL these methods.
-sub install_impl {
-	my $self=shift;
-	my $destdir=shift;
-	1;
-}
-
-sub clean_impl {
-	my $self=shift;
-	1;
-}
-
-package Debian::Debhelper::Dh_Buildsystem_Option;
-
-use Debian::Debhelper::Dh_Buildsystems qw( DEFAULT_BUILD_DIRECTORY );
-use base 'Debian::Debhelper::Dh_Buildsystem_Basic';
-
-# Derived class can call this method in its constructor to enforce
-# outside-source building even if the user didn't request it.
-#
-# XXX JEH is there a reason for this to be in
-# Dh_Buildsystem_Option instead of the base class?
-sub enforce_outside_source_building {
-	my ($self, $builddir) = @_;
-	if (!defined $self->{builddir}) {
-		$self->{builddir} = ($builddir && $builddir ne ".") ? $builddir : DEFAULT_BUILD_DIRECTORY;
-	}
-}
-
-# Constructs option to be passed to the source package buildsystem to
-# change build directory. Returns nothing by default.
-sub get_builddir_option {
-	my $self=shift;
-	return;
-}
-
-# XXX JEH if the reasoning for removing invoke_impl from above is followed,
-# then this whole derived class ends up not being needed.
-sub invoke_impl {
-	my $self=shift;
-	my $method=shift;
-
-	if ($self->get_builddir_option()) {
-		return $self->SUPER::invoke_impl($method, $self->get_builddir_option(), @_);
-	}
-	else {
-		return $self->SUPER::invoke_impl($method, @_);
-	}
-}
-
-package Debian::Debhelper::Dh_Buildsystem_Chdir;
-
-# XXX JEH I'm very leery of code that chdirs, it can be very hard to follow
-# and cause a lot of mess. (As we'll see in the buildsystem modules that
-# use this class.) It seems to me that this entire class could be
-# basically replaced by a doit_in_builddir() function.
-
-use Cwd;
-use File::Spec;
-use Debian::Debhelper::Dh_Lib;
-use base 'Debian::Debhelper::Dh_Buildsystem_Option';
-
-sub new {
-	my $cls=shift;
-	my $self=$cls->SUPER::new(@_);
-	$self->{topdir} = '.';
-	return $self;
-}
-
-sub _cd {
-	my ($cls, $dir) = @_;
-	verbose_print("cd '$dir'");
-	if (! $dh{NO_ACT}) {
-		chdir $dir or error("error: unable to chdir to $dir");
-	}
-}
-
-sub _mkdir {
-	my ($cls, $dir) = @_;
-	if (-e $dir && ! -d $dir) {
-		error("error: unable to create '$dir': object already exists and is not a directory");
-	}
-	else {
-		verbose_print("mkdir '$dir'");
-		if (! $dh{NO_ACT}) {
-			mkdir($dir, 0755) or error("error: unable to create '$dir': $!");
-		}
-		return 1;
-	}
-	return 0;
-}
-
-sub get_builddir {
-	my $self=shift;
-	if (defined $self->{builddir} && $self->{topdir} ne ".") {
-		return File::Spec->catfile($self->{topdir}, $self->{builddir});
-	}
-	return $self->SUPER::get_builddir();
-}
-
-sub get_topdir {
-	my $self=shift;
-	if ($self->{topdir} ne ".") {
-		return File::Spec->abs2rel($self->{topdir});
-	}
-	return $self->{topdir};
-}
-
-sub get_toppath {
-	my ($self, $path) = @_;
-	return File::Spec->catfile($self->get_topdir(), $path);
-}
-
-sub cd {
-	my $self = shift;
-	if ($self->get_builddir() && $self->{topdir} ne ".") {
-		$self->_cd($self->get_topdir());
-		$self->{topdir} = ".";
-		return 1;
-	}
-	return 0;
-}
-
-sub cd_to_builddir {
-	my $self = shift;
-	if ($self->get_builddir() && $self->{topdir} eq ".") {
-		$self->{topdir} = getcwd();
-		$self->_cd($self->get_builddir());
-		return 1;
-	}
-	return 0;
-}
-
-sub exec_in_topdir {
-	my $self=shift;
-	my $sub=shift;
-	my $ret;
-
-	if ($self->get_topdir() ne ".") {
-		$self->cd();
-		$ret = &$sub(@_);
-		$self->cd_to_builddir();
-	}
-	else {
-		$ret = &$sub(@_);
-	}
-	return $ret;
-}
-
-# *_impl() is run with current working directory changed to the
-# build directory if requested.
-sub invoke_impl {
-	my $self=shift;
-	my $method=shift;
-	my $ret;
-
-	$self->cd_to_builddir();
-	$ret = $self->$method(@_);
-	$self->cd();
-	return $ret;
-}
-
-sub configure {
-	my $self=shift;
-	if ($self->get_builddir()) {
-		$self->_mkdir($self->get_builddir());
-	}
-	return $self->SUPER::configure(@_);
-}
-
-# If outside-source tree building is done, whole build directory
-# gets wiped out by default. Otherwise, clean_impl() is called.
-sub clean {
-	my $self=shift;
-	if ($self->get_builddir()) {
-		if (-d $self->get_builddir()) {
-			$self->cd();
-			doit("rm", "-rf", $self->get_builddir());
-			return 1;
-		}
-	} else {
-		return $self->SUPER::clean(@_);
-	}
-}
-
-1;
diff --git a/Debian/Debhelper/Dh_Buildsystem_Basic.pm b/Debian/Debhelper/Dh_Buildsystem_Basic.pm
new file mode 100644
index 00000000..cd4e448f
--- /dev/null
+++ b/Debian/Debhelper/Dh_Buildsystem_Basic.pm
@@ -0,0 +1,277 @@
+# Defines basic debhelper buildsystem class interface.
+#
+# Copyright: © 2008-2009 Modestas Vainius
+# License: GPL-2+
+
+package Debian::Debhelper::Dh_Buildsystem_Basic;
+
+use strict;
+use warnings;
+use Cwd;
+use File::Spec;
+use Debian::Debhelper::Dh_Lib;
+
+# Build system name. Defaults to the last component of the class
+# name. Do not override this method unless you know what you are
+# doing.
+sub NAME {
+	my $self=shift;
+	my $cls = ref($self) || $self;
+	if ($cls =~ m/^.+::([^:]+)$/) {
+		return $1;
+	}
+	else {
+		error("ınvalid buildsystem class name: $cls");
+	}
+}
+
+# Description of the build system to be shown to the users.
+sub DESCRIPTION {
+	"basic debhelper build system class (please provide description)";
+}
+
+# Default build directory. Can be overriden in the derived
+# class if really needed.
+sub DEFAULT_BUILD_DIRECTORY {
+	"obj-" . dpkg_architecture_value("DEB_BUILD_GNU_TYPE");
+}
+
+# XXX JEH Turns out that one build system overrides this method,
+# perl_build uses it to set an env vatiable before each method
+# call. But that's unnecessary; it could just set it in its constructor.
+# XXX MDX See comment below. is_auto is currently unused but I think it
+# is a good addition to the API for future cases.
+
+# Constructs a new build system object. Named parameters:
+# - builddir - specifies build directory to use. If not specified,
+#              in-source build will be performed. If undef or empty,
+#              default DEFAULT_BUILD_DIRECTORY will be used.
+# - is_auto -  might be used by the derived classes to determine if
+#              the build system has been picked up automatically.
+# Derived class can override the constructor to initialize common parameters.
+# Constructor SHOULD NOT be used to initialize build environment because
+# constructed class may not be eventually used to build the package (if e.g.
+# is_auto_buildable() returns 0).
+sub new {
+	my ($cls, %opts)=@_;
+
+	my $self = bless({ builddir => undef, is_auto => $opts{is_auto} }, $cls);
+	if (exists $opts{builddir}) {
+		if ($opts{builddir}) {
+			$self->{builddir} = $opts{builddir};
+		}
+		else {
+			$self->{builddir} = $self->DEFAULT_BUILD_DIRECTORY();
+		}
+	}
+	return $self;
+}
+
+# This instance method is called to check if the build system is capable
+# to auto build a source package. Additional argument $action describes
+# which operation the caller is going to perform (either configure,
+# build, test, install or clean). You must override this method for the
+# build system module to be ever picked up automatically. This method is
+# used in conjuction with @Dh_Buildsystems::BUILDSYSTEMS.
+#
+# This method is supposed to be called with source root directory being
+# working directory. Use $self->get_buildpath($path) method to get full
+# path to the files in the build directory.
+sub is_auto_buildable {
+	my $self=shift;
+	my ($action) = @_;
+	return 0;
+}
+
+# Derived class can call this method in its constructor
+# to enforce in-source building even if the user requested otherwise.
+sub enforce_in_source_building {
+	my $self=shift;
+	if ($self->{builddir}) {
+		# Since this method is called in the constructor, emitting
+		# warnings immediatelly may cause too much noise when
+		# scanning for auto buildsystems or listing them.
+		push @{$self->{warnings}},
+		    $self->NAME()." buildsystem does not support building outside-source. In-source build enforced.";
+		$self->{builddir} = undef;
+	}
+}
+
+# Derived class can call this method in its constructor to enforce
+# outside-source building even if the user didn't request it.
+sub enforce_outside_source_building {
+	my ($self, $builddir) = @_;
+	if (!defined $self->{builddir}) {
+		$self->{builddir} = ($builddir && $builddir ne ".") ? $builddir : $self->DEFAULT_BUILD_DIRECTORY();
+	}
+}
+
+# Get path to the specified build directory
+sub get_builddir {
+	my $self=shift;
+	return $self->{builddir};
+}
+
+# Construct absolute path to the file from the given path that is relative
+# to the build directory.
+sub get_buildpath {
+	my ($self, $path) = @_;
+	if ($self->get_builddir()) {
+		return File::Spec->catfile($self->get_builddir(), $path);
+	}
+	else {
+		return File::Spec->catfile('.', $path);
+	}
+}
+
+# When given a relative path in the source tree, converts it
+# to the path that is relative to the build directory.
+# If $path is not given, returns relative path to the root of the
+# source tree from the build directory.
+sub get_rel2builddir_path {
+	my $self=shift;
+	my $path=shift;
+
+	if (defined $path) {
+		$path = File::Spec->catfile(Cwd::getcwd(), $path);
+	}
+	else {
+		$path = Cwd::getcwd();
+	}
+	if ($self->get_builddir()) {
+		return File::Spec->abs2rel($path, Cwd::abs_path($self->get_builddir()));
+	}
+	return $path;
+}
+
+# XXX JEH I'm very leery of code that chdirs, it can be very hard to follow
+# and cause a lot of mess. (As we'll see in the buildsystem modules that
+# use this class.) It seems to me that this entire class could be
+# basically replaced by a doit_in_builddir() function.
+# XXX MDX implemented.
+
+sub _mkdir {
+	my ($cls, $dir)=@_;
+	if (-e $dir && ! -d $dir) {
+		error("error: unable to create '$dir': object already exists and is not a directory");
+	}
+	elsif (! -d $dir) {
+		verbose_print("mkdir '$dir'");
+		if (! $dh{NO_ACT}) {
+			mkdir($dir, 0755) or error("error: unable to create '$dir': $!");
+		}
+		return 1;
+	}
+	return 0;
+}
+
+sub _cd {
+	my ($cls, $dir)=@_;
+	if (! $dh{NO_ACT}) {
+		chdir $dir or error("error: unable to chdir to $dir");
+	}
+}
+
+# Creates a build directory. Returns 1 if the directory was created
+# or 0 if it already exists or there is no need to create it.
+sub mkdir_builddir {
+	my $self=shift;
+	if ($self->get_builddir()) {
+		return $self->_mkdir($self->get_builddir());
+	}
+	return 0;
+}
+
+# Changes working directory the build directory (if needed), calls doit(@_)
+# and changes working directory back to the source directory.
+sub doit_in_builddir {
+	my $self=shift;
+	if ($self->get_builddir()) {
+		my $builddir = $self->get_builddir();
+		my $sourcedir = $self->get_rel2builddir_path();
+		verbose_print("cd to the build directory: $builddir");
+		$self->_cd($builddir);
+		doit(@_);
+		verbose_print("cd back to the source directory: $sourcedir");
+		$self->_cd($sourcedir);
+	}
+	else {
+		doit(@_);
+	}
+	return 1;
+}
+
+# In case of outside-source tree building, whole build directory
+# gets wiped (if it exists) and 1 is returned. Otherwise, nothing
+# is done and 0 is returned.
+sub clean_builddir {
+	my $self=shift;
+	if ($self->get_builddir()) {
+		if (-d $self->get_builddir()) {
+			doit("rm", "-rf", $self->get_builddir());
+		}
+		return 1;
+	}
+	return 0;
+}
+
+
+# Instance method that is called before performing any action (see below).
+# Action name is passed as an argument. Derived classes overriding this
+# method should also call SUPER implementation of it.
+sub pre_action {
+	my $self=shift;
+	my $action=shift;
+
+	# Emit warnings pre action.
+	if (exists $self->{warnings}) {
+		for my $msg (@{$self->{warnings}}) {
+			warning("warning: " . $msg);
+		}
+	}
+}
+
+# Instance method that is called after performing any action (see below).
+# Action name is passed as an argument. Derived classes overriding this
+# method should also call SUPER implementation of it.
+sub post_action {
+	my $self=shift;
+	my $action=shift;
+}
+
+# The instance methods below provide support for configuring,
+# building, testing, install and cleaning source packages.
+# In case of failure, the method may just error() out.
+#
+# These methods should be overriden by derived classes to
+# implement buildsystem specific actions needed to build the
+# source. Arbitary number of custom action arguments might be
+# passed. Default implementations do nothing.
+sub configure {
+	my $self=shift;
+}
+
+sub build {
+	my $self=shift;
+}
+
+sub test {
+	my $self=shift;
+}
+
+# destdir parameter specifies where to install files.
+# XXX JEH I don't see where this destdir parameter is passed in
+# to a call to $object->install ? In Dh_Buildsystems it does:
+#                 return $buildsystem->$toolname(@_, @{$dh{U_PARAMS}});
+# Which passes a different parameter, to ALL these methods.
+# XXX MDX destdir is used in the dh_auto_install tool.
+sub install {
+	my $self=shift;
+	my $destdir=shift;
+}
+
+sub clean {
+	my $self=shift;
+}
+
+1;
diff --git a/Debian/Debhelper/Dh_Buildsystems.pm b/Debian/Debhelper/Dh_Buildsystems.pm
index aa2dff99..676551b9 100644
--- a/Debian/Debhelper/Dh_Buildsystems.pm
+++ b/Debian/Debhelper/Dh_Buildsystems.pm
@@ -1,4 +1,5 @@
 # A module for loading and managing debhelper buildsystem plugins.
+# This module is intended to be used by all dh_auto_* helper commands.
 #
 # Copyright: © 2009 Modestas Vainius
 # License: GPL-2+
@@ -9,124 +10,67 @@ use strict;
 use warnings;
 use Debian::Debhelper::Dh_Lib;
 
-use Exporter qw( import );
-our @EXPORT_OK = qw( DEFAULT_BUILD_DIRECTORY );
+use base 'Exporter';
+our @EXPORT=qw(&buildsystems_init &buildsystems_do &load_buildsystem);
 
-# IMPORTANT: more specific buildsystems should go first
 # XXX JEH as noted, this has to match historical order for back-compat
-my @BUILDSYSTEMS = (
+# XXX MDX Current dh_auto_* look like:
+# configure: autotools, perl_makemaker, perl_build
+# build:     makefile, python_distutils, perl_build
+# test:      makefile, perl_build
+# install:   makefile (with perl_makermaker) hack, python_distutils, perl_build
+# clean:     makefile, python_distutils, perl_build
+# So historical @BUILDSYSTEMS order (as per autodetection, see
+# is_auto_buildable() of the respective classes):
+#   autotools (+configure; the rest - next class)
+#   python_distutils (+build +install +clean; the rest - next class)
+#   perl_makemaker (+configure +install (special hack); the rest - next class)
+#   makefile (+build +test +install +clean; configure - next class)
+#   perl_build (handles everything)
+
+# Historical order must be kept for backwards compatibility. New
+# buildsystems MUST be added to the END of the list.
+our @BUILDSYSTEMS = (
     "autotools",
-    "cmake",
-    "perl_build",
-    "perl_makefile",
     "python_distutils",
+    "perl_makemaker",
     "makefile",
+    "perl_build",
+    "cmake",
 );
 
-sub DEFAULT_BUILD_DIRECTORY {
-	return "obj-" . dpkg_architecture_value("DEB_BUILD_GNU_TYPE");
-}
-
-sub new {
-	my $cls=shift;
-	my %opts=@_;
-	my $self = bless({
-	    'o_dir' => undef,
-	    'o_system' => undef,
-	    'loaded_buildsystems' => [] }, $cls);
-
-	# XXX JEH AFAICS, these 2 env variables are never used or documented
-	if (!exists $opts{noenv}) {
-		if (exists $ENV{DH_AUTO_BUILDDIRECTORY}) {
-			$self->_set_build_directory_option("env", $ENV{DH_AUTO_BUILDDIRECTORY});
-		}
-		if (exists $ENV{DH_AUTO_BUILDSYSTEM}) {
-			$self->{o_system} = $ENV{DH_AUTO_BUILDSYSTEM};
-		}
-	}
-	return $self;
-}
-
-sub get_options {
-	my $self=shift;
-	my @options=@_;
-
-	my $set_dir = sub { $self->_set_build_directory_option(@_) };
-	my $list_bs = sub { $self->list_buildsystems(@_); exit 0 };
-
-	push @options, (
-	    "b:s" => $set_dir,
-	    "build-directory:s" => $set_dir,
-	    "builddirectory:s" => $set_dir,
-
-	    "m=s" => \$self->{o_system},
-	    "build-system=s" => \$self->{o_system},
-	    "buildsystem=s" => \$self->{o_system},
-
-	    "l" => $list_bs,
-	    "--list" => $list_bs,
-	);
-	my %options = @options;
-	return \%options;
-}
-
-sub _set_build_directory_option {
-	# XXX JEH option argument is not used, would be less confusing to
-	# not pass extra getopt value in
-	my ($self, $option, $value) = @_;
-	if (!$value || $value eq "auto") {
-		# Autogenerate build directory name
-		$self->{o_dir} = DEFAULT_BUILD_DIRECTORY;
-	}
-	else {
-		$self->{o_dir} = $value;
-	}
-}
+sub create_buildsystem_instance {
+	my $system=shift;
+	my %bsopts=@_;
+	my $module = "Debian::Debhelper::Buildsystem::$system";
 
-# XXX JEH this sub is not used
-sub _dump_options {
-	my $self=shift;
-	for my $opt (qw(o_dir o_system)) {
-		if (defined $self->{$opt}) {
-			print $opt, ": ", $self->{$opt}, "\n";
-		}
+	eval "use $module";
+	if ($@) {
+		error("unable to load buildsystem class '$system': $@");
 	}
-}
-
-sub _get_buildsystem_module {
-	my ($self, $system) = @_;
-	my $module = "Debian::Debhelper::Buildsystem::$system";
 
-	if (grep $module, @{$self->{loaded_buildsystems}} == 0) {
-		eval "use $module";
-		if ($@) {
-			error("Unable to load buildsystem '$system': $@");
-		}
-		push @{$self->{loaded_buildsystems}}, $module;
+	if (!exists $bsopts{builddir} && exists $dh{BUILDDIR}) {
+		$bsopts{builddir} = $dh{BUILDDIR};
 	}
-	return $module;
+	return $module->new(%bsopts);
 }
 
 sub load_buildsystem {
 	# XXX JEH the $system param is never passed
 	# by any call to this function
-	my ($self, $action, $system) = @_;
-
-	if (!defined $system) {
-		$system = $self->{o_system};
-	}
+	# XXX MDX Yes, it was sort of redudant. But see buildsystems_do() now.
+	my ($action, $system)=@_;
 	if (defined $system) {
-		my $module =  $self->_get_buildsystem_module($system);
-		verbose_print("Selected buildsystem (specified): ".$module->NAME());
-		return $module->new($self->{o_dir});
+		my $inst = create_buildsystem_instance($system);
+		verbose_print("Selected buildsystem (specified): ".$inst->NAME());
+		return $inst;
 	}
 	else {
 		# Try to determine build system automatically
 		for $system (@BUILDSYSTEMS) {
-			my $module = $self->_get_buildsystem_module($system);
-			my $inst = $module->new($self->{o_dir});
-			if ($inst->is_buildable($action)) {
-				verbose_print("Selected buildsystem (auto): ".$module->NAME());
+			my $inst = create_buildsystem_instance($system, is_auto=>1);
+			if ($inst->is_auto_buildable($action)) {
+				verbose_print("Selected buildsystem (auto): ". $inst->NAME());
 				return $inst;
 			}
 		}
@@ -134,48 +78,67 @@ sub load_buildsystem {
 	return;
 }
 
-sub load_all_buildsystems {
-	my $self=shift;
+sub list_buildsystems {
 	for my $system (@BUILDSYSTEMS) {
-		$self->_get_buildsystem_module($system);
+		my $inst = create_buildsystem_instance($system);
+		printf("%s - %s.\n", $inst->NAME(), $inst->DESCRIPTION());
 	}
-	return @{$self->{loaded_buildsystems}};
 }
 
-sub list_buildsystems {
-	my $self=shift;
-	for my $system ($self->load_all_buildsystems()) {
-		printf("%s - %s.\n", $system->NAME(), $system->DESCRIPTION());
+sub buildsystems_init {
+	my %args=@_;
+
+	# XXX JEH AFAICS, these 2 env variables are never used or documented
+	# XXX MDX They are used (see below), not documented though.
+	# TODO: Not documented in the manual pages yet.
+	# Initialize options from environment variables
+	if (exists $ENV{DH_AUTO_BUILDDIRECTORY}) {
+		$dh{BUILDDIR} = $ENV{DH_AUTO_BUILDDIRECTORY};
 	}
-}
+	if (exists $ENV{DH_AUTO_BUILDSYSTEM}) {
+		$dh{BUILDSYS} = $ENV{DH_AUTO_BUILDSYSTEM};
+	}
+
+	# Available command line options
+	my $list_bs = sub { list_buildsystems(); exit 0 };
+	my $set_builddir = sub { $dh{BUILDDIR} = $_[1] };
+	my %options = (
+	    "b:s" => $set_builddir,
+	    "build-directory:s" => $set_builddir,
+	    "builddirectory:s" => $set_builddir,
 
-sub init_dh_auto_tool {
-	my $self=shift;
+	    "m=s" => \$dh{BUILDSYS},
+	    "build-system=s" => \$dh{BUILDSYS},
+	    "buildsystem=s" => \$dh{BUILDSYS},
 
-	Debian::Debhelper::Dh_Lib::init(
-	    options => $self->get_options(@_));
-	$self->{initialized}=1;
+	    "l" => $list_bs,
+	    "--list" => $list_bs,
+	);
+	map { $args{options}{$_} = $options{$_} } keys(%options);
+	Debian::Debhelper::Dh_Lib::init(%args);
 }
 
-sub run_dh_auto_tool {
-	my $self=shift;
-	my $toolname = basename($0);
-	my $buildsystem;
+sub buildsystems_do {
+	my $action=shift;
 
-	# XXX JEH does this if ever not fire?
-	if (!exists $self->{initialized}) {
-		$self->init_dh_auto_tool();
+	if (!defined $action) {
+		$action = basename($0);
+		$action =~ s/^dh_auto_//;
 	}
 
-	# Guess action from the dh_auto_* name
-	$toolname =~ s/^dh_auto_//;
-	if (grep(/^\Q$toolname\E$/, qw{configure build test install clean}) == 0) {
-		error("Unrecognized dh auto tool: ".basename($0));
+	# XXX JEH does this if ever not fire?
+	# XXX MDX See dh_auto_install. I'm removing this anyway
+	# and making buildsystem_init() call in dh_auto_* mandatory.
+
+	if (grep(/^\Q$action\E$/, qw{configure build test install clean}) == 0) {
+		error("unrecognized auto action: ".basename($0));
 	}
 
-	$buildsystem = $self->load_buildsystem($toolname);
+	my $buildsystem = load_buildsystem($action, $dh{BUILDSYS});
 	if (defined $buildsystem) {
-		return $buildsystem->$toolname(@_, @{$dh{U_PARAMS}});
+		$buildsystem->pre_action($action);
+		$buildsystem->$action(@_, @{$dh{U_PARAMS}});
+		$buildsystem->post_action($action);
 	}
 	return 0;
 }
@@ -186,5 +149,10 @@ sub run_dh_auto_tool {
 # that parses the command line, loads the specified system, and uses it,
 # passing it the build directory. It would be both shorter and easier to
 # understand.
+# XXX I refactored this into a module rather than OO class. I do not agree
+# about a single sub though as it is more complicated than that and
+# I think it is more clear to have the code segmented a bit. See also
+# dh_auto_install why both buildsystems_init() and buildsystems_do()
+# are needed.
 
 1;
diff --git a/dh_auto_build b/dh_auto_build
index 9cfe70ef..56b9b5f0 100755
--- a/dh_auto_build
+++ b/dh_auto_build
@@ -37,8 +37,8 @@ or override any standard parameters that dh_auto_build passes.
 
 =cut
 
-my $manager = new Debian::Debhelper::Dh_Buildsystems;
-$manager->run_dh_auto_tool();
+buildsystems_init();
+buildsystems_do();
 
 =head1 SEE ALSO
 
diff --git a/dh_auto_clean b/dh_auto_clean
index 75f3ce48..1b7d46cd 100755
--- a/dh_auto_clean
+++ b/dh_auto_clean
@@ -38,8 +38,8 @@ or override the any standard parameters that dh_auto_clean passes.
 
 =cut
 
-my $manager = new Debian::Debhelper::Dh_Buildsystems;
-$manager->run_dh_auto_tool();
+buildsystems_init();
+buildsystems_do();
 
 =head1 SEE ALSO
 
diff --git a/dh_auto_configure b/dh_auto_configure
index e846e999..416c25b3 100755
--- a/dh_auto_configure
+++ b/dh_auto_configure
@@ -38,8 +38,8 @@ or override the standard parameters that dh_auto_configure passes.
 
 =cut
 
-my $manager = new Debian::Debhelper::Dh_Buildsystems;
-$manager->run_dh_auto_tool();
+buildsystems_init();
+buildsystems_do();
 
 =head1 SEE ALSO
 
diff --git a/dh_auto_install b/dh_auto_install
index c115a184..db2c6e90 100755
--- a/dh_auto_install
+++ b/dh_auto_install
@@ -49,8 +49,7 @@ or override the any standard parameters that dh_auto_install passes.
 
 =cut
 
-my $manager = new Debian::Debhelper::Dh_Buildsystems;
-$manager->init_dh_auto_tool();
+buildsystems_init();
 
 my $destdir;
 my @allpackages=getpackages();
@@ -62,7 +61,7 @@ else {
 }
 $destdir=cwd()."/".$destdir;
 
-$manager->run_dh_auto_tool($destdir);
+buildsystems_do("install", $destdir);
 
 =head1 SEE ALSO
 
diff --git a/dh_auto_test b/dh_auto_test
index 9dda30fb..e68bf09a 100755
--- a/dh_auto_test
+++ b/dh_auto_test
@@ -48,8 +48,8 @@ if (defined $ENV{DEB_BUILD_OPTIONS} && $ENV{DEB_BUILD_OPTIONS} =~ /nocheck/) {
 	exit 0;
 }
 
-my $manager = new Debian::Debhelper::Dh_Buildsystems;
-$manager->run_dh_auto_tool();
+buildsystems_init();
+buildsystems_do();
 
 =head1 SEE ALSO