new directive: conflicts() (#3125)

* Add conflicts(<spec>) directive
* openblas: added conflicts for intel@16 refs #3119
* added brief docs and unit tests

var/spack/repos/builtin.mock/packages/conflict-parent/package.py

@@ -0,0 +1,46 @@
+##############################################################################
+# Copyright (c) 2013-2016, Lawrence Livermore National Security, LLC.
+# Produced at the Lawrence Livermore National Laboratory.
+#
+# This file is part of Spack.
+# Created by Todd Gamblin, tgamblin@llnl.gov, All rights reserved.
+# LLNL-CODE-647188
+#
+# For details, see https://github.com/llnl/spack
+# Please also see the LICENSE file for our notice and the LGPL.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU Lesser General Public License (as
+# published by the Free Software Foundation) version 2.1, February 1999.
+#
+# This program is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the IMPLIED WARRANTY OF
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the terms and
+# conditions of the GNU Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public
+# License along with this program; if not, write to the Free Software
+# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+##############################################################################
+from spack import *
+
+
+class ConflictParent(Package):
+    homepage = 'https://github.com/tgamblin/callpath'
+    url = 'http://github.com/tgamblin/callpath-1.0.tar.gz'
+
+    version(0.8, 'foobarbaz')
+    version(0.9, 'foobarbaz')
+    version(1.0, 'foobarbaz')
+
+    depends_on('conflict')
+
+    conflicts('^conflict~foo', when='@0.9')
+
+    def install(self, spec, prefix):
+        configure("--prefix=%s" % prefix)
+        make()
+        make("install")
+
+    def setup_environment(self, senv, renv):
+        renv.set('FOOBAR', self.name)

var/spack/repos/builtin.mock/packages/conflict/package.py

@@ -0,0 +1,46 @@
+##############################################################################
+# Copyright (c) 2013-2016, Lawrence Livermore National Security, LLC.
+# Produced at the Lawrence Livermore National Laboratory.
+#
+# This file is part of Spack.
+# Created by Todd Gamblin, tgamblin@llnl.gov, All rights reserved.
+# LLNL-CODE-647188
+#
+# For details, see https://github.com/llnl/spack
+# Please also see the LICENSE file for our notice and the LGPL.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU Lesser General Public License (as
+# published by the Free Software Foundation) version 2.1, February 1999.
+#
+# This program is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the IMPLIED WARRANTY OF
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the terms and
+# conditions of the GNU Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public
+# License along with this program; if not, write to the Free Software
+# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+##############################################################################
+from spack import *
+
+
+class Conflict(Package):
+    homepage = 'https://github.com/tgamblin/callpath'
+    url = 'http://github.com/tgamblin/callpath-1.0.tar.gz'
+
+    version(0.8, 'foobarbaz')
+    version(0.9, 'foobarbaz')
+    version(1.0, 'foobarbaz')
+
+    variant('foo', default=True, description='')
+
+    conflicts('%clang', when='+foo')
+
+    def install(self, spec, prefix):
+        configure("--prefix=%s" % prefix)
+        make()
+        make("install")
+
+    def setup_environment(self, senv, renv):
+        renv.set('FOOBAR', self.name)

var/spack/repos/builtin/packages/openblas/package.py

@@ -59,6 +59,8 @@ class Openblas(MakefilePackage):
 
     parallel = False
 
+    conflicts('%intel@16', when='@0.2.15:0.2.19')
+
     @run_before('edit')
     def check_compilers(self):
         # As of 06/2016 there is no mechanism to specify that packages which