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, 2 insertions, 2 deletions

diff --git a/Debian/Debhelper/Buildsystem/autoconf.pm b/Debian/Debhelper/Buildsystem/autoconf.pm
index a97de9c6..d7b0bed2 100644
--- a/Debian/Debhelper/Buildsystem/autoconf.pm
+++ b/Debian/Debhelper/Buildsystem/autoconf.pm
@@ -18,9 +18,9 @@ sub check_auto_buildable {
 	my $this=shift;
 	my ($step)=@_;
 
-	# Handle configure; the rest - next class
+	# Handle configure; the rest - next class (compat with 7.0.x code path)
 	if ($step eq "configure") {
-		return -x $this->get_sourcepath("configure");
+		return 1 if -x $this->get_sourcepath("configure");
 	}
 	return 0;
 }