Improve build system auto-selection process

This patch alters semantics of check_auto_buildable() a bit. Now it can
also indicate if the source has already been partitially built with the
build system and if so, such build system may be auto-selected over a less
specific its parent (in the inheritance tree) even if the latter is earlier
in the @BUILDSYSTEMS array.

However, this still leaves a requirement that a derivative build system
must not do anything that may break packages of the parent build system.
Otherwise, introduction of a new derivative build system might break
packages which already had that build system implemented via overrides...

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

1 files changed, 5 insertions, 9 deletions

diff --git a/Debian/Debhelper/Buildsystem/makefile.pm b/Debian/Debhelper/Buildsystem/makefile.pm
index 704f9c95..083abc42 100644
--- a/Debian/Debhelper/Buildsystem/makefile.pm
+++ b/Debian/Debhelper/Buildsystem/makefile.pm
@@ -71,15 +71,11 @@ sub check_auto_buildable {
 	my $this=shift;
 	my ($step) = @_;
 
-	# Handles build, test, install, clean; configure - next class
-	if (grep /^\Q$step\E$/, qw{build test install clean}) {
-		# This is always called in the source directory, but generally
-		# Makefiles are created (or live) in the the build directory.
-		return -e $this->get_buildpath("Makefile") ||
-		       -e $this->get_buildpath("makefile") ||
-		       -e $this->get_buildpath("GNUmakefile");
-	}
-	return 0;
+	# This is always called in the source directory, but generally
+	# Makefiles are created (or live) in the the build directory.
+	return (-e $this->get_buildpath("Makefile") ||
+	        -e $this->get_buildpath("makefile") ||
+	        -e $this->get_buildpath("GNUmakefile")) ? 1 : 0;
 }
 
 sub build {