Merge branch 'features/optional-deps' into develop

This includes:
- Much better variant support (+debug/-debug)
- Optional dependency support (depends_on(... , when='<condition>')
- New config file format (YAML in ~/.spack)
- New Spec format (YAML in $prefix/.spack/spec.yaml)

var/spack/mock_configs/site_spackconfig

@@ -1,12 +0,0 @@
-[compiler "gcc@4.5.0"]
-    cc  = /path/to/gcc
-    cxx = /path/to/g++
-    f77 = /path/to/gfortran
-    fc  = /path/to/gfortran
-
-[compiler "clang@3.3"]
-    cc  = /path/to/clang
-    cxx = /path/to/clang++
-    f77 = None
-    fc  = None
-

var/spack/mock_configs/site_spackconfig/compilers.yaml

@@ -0,0 +1,12 @@
+compilers:
+  all:
+    clang@3.3:
+      cc: /path/to/clang
+      cxx: /path/to/clang++
+      f77: None
+      fc: None
+    gcc@4.5.0:
+      cc: /path/to/gcc
+      cxx: /path/to/g++
+      f77: /path/to/gfortran
+      fc: /path/to/gfortran

var/spack/mock_packages/a/package.py

@@ -0,0 +1,12 @@
+from spack import *
+
+class A(Package):
+    """Simple package with no dependencies"""
+
+    homepage = "http://www.example.com"
+    url      = "http://www.example.com/a-1.0.tar.gz"
+
+    version('1.0', '0123456789abcdef0123456789abcdef')
+
+    def install(self, spec, prefix):
+        pass

var/spack/mock_packages/b/package.py

@@ -0,0 +1,12 @@
+from spack import *
+
+class B(Package):
+    """Simple package with no dependencies"""
+
+    homepage = "http://www.example.com"
+    url      = "http://www.example.com/b-1.0.tar.gz"
+
+    version('1.0', '0123456789abcdef0123456789abcdef')
+
+    def install(self, spec, prefix):
+        pass

var/spack/mock_packages/c/package.py

@@ -0,0 +1,12 @@
+from spack import *
+
+class C(Package):
+    """Simple package with no dependencies"""
+
+    homepage = "http://www.example.com"
+    url      = "http://www.example.com/c-1.0.tar.gz"
+
+    version('1.0', '0123456789abcdef0123456789abcdef')
+
+    def install(self, spec, prefix):
+        pass

var/spack/mock_packages/e/package.py

@@ -0,0 +1,12 @@
+from spack import *
+
+class E(Package):
+    """Simple package with no dependencies"""
+
+    homepage = "http://www.example.com"
+    url      = "http://www.example.com/e-1.0.tar.gz"
+
+    version('1.0', '0123456789abcdef0123456789abcdef')
+
+    def install(self, spec, prefix):
+        pass

var/spack/mock_packages/mpich/package.py

@@ -30,6 +30,9 @@ class Mpich(Package):
     list_url   = "http://www.mpich.org/static/downloads/"
     list_depth = 2
 
+    variant('debug', default=False,
+            description="Compile MPICH with debug flags.")
+
     version('3.0.4', '9c5d5d4fe1e17dd12153f40bc5b6dbc0')
     version('3.0.3', 'foobarbaz')
     version('3.0.2', 'foobarbaz')

var/spack/mock_packages/mpileaks/package.py

@@ -33,6 +33,9 @@ class Mpileaks(Package):
     version(2.2, 'foobarbaz')
     version(2.3, 'foobarbaz')
 
+    variant('debug', default=False, description='Debug variant')
+    variant('opt',   default=False, description='Optimized variant')
+
     depends_on("mpi")
     depends_on("callpath")
 

var/spack/mock_packages/optional-dep-test-2/package.py

@@ -0,0 +1,18 @@
+from spack import *
+
+class OptionalDepTest2(Package):
+    """Depends on the optional-dep-test package"""
+
+    homepage = "http://www.example.com"
+    url      = "http://www.example.com/optional-dep-test-2-1.0.tar.gz"
+
+    version('1.0', '0123456789abcdef0123456789abcdef')
+
+    variant('odt', default=False)
+    variant('mpi', default=False)
+
+    depends_on('optional-dep-test', when='+odt')
+    depends_on('optional-dep-test+mpi', when='+mpi')
+
+    def install(self, spec, prefix):
+        pass

var/spack/mock_packages/optional-dep-test/package.py

@@ -0,0 +1,29 @@
+from spack import *
+
+class OptionalDepTest(Package):
+    """Description"""
+
+    homepage = "http://www.example.com"
+    url      = "http://www.example.com/optional_dep_test-1.0.tar.gz"
+
+    version('1.0', '0123456789abcdef0123456789abcdef')
+    version('1.1', '0123456789abcdef0123456789abcdef')
+
+    variant('a',   default=False)
+    variant('f',   default=False)
+    variant('mpi', default=False)
+
+    depends_on('a', when='+a')
+    depends_on('b', when='@1.1')
+    depends_on('c', when='%intel')
+    depends_on('d', when='%intel@64.1')
+    depends_on('e', when='%clang@34:40')
+
+    depends_on('f', when='+f')
+    depends_on('g', when='^f')
+    depends_on('mpi', when='^g')
+
+    depends_on('mpi', when='+mpi')
+
+    def install(self, spec, prefix):
+        pass

var/spack/packages/python/package.py

@@ -139,7 +139,9 @@ def write_easy_install_pth(self, exts):
 
 
     def activate(self, ext_pkg, **args):
-        args.update(ignore=self.python_ignore(ext_pkg, args))
+        ignore=self.python_ignore(ext_pkg, args)
+        args.update(ignore=ignore)
+
         super(Python, self).activate(ext_pkg, **args)
 
         exts = spack.install_layout.extension_map(self.spec)