Add spack arch --operating-system and --target flags

lib/spack/spack/cmd/arch.py

@@ -35,11 +35,24 @@ def setup_parser(subparser):
     parts = subparser.add_mutually_exclusive_group()
     parts.add_argument(
         '-p', '--platform', action='store_true', default=False,
-        help="print only the platform")
+        help='print only the platform')
+    parts.add_argument(
+        '-o', '--operating-system', action='store_true', default=False,
+        help='print only the operating system')
+    parts.add_argument(
+        '-t', '--target', action='store_true', default=False,
+        help='print only the target')
 
 
 def arch(parser, args):
+    arch = architecture.Arch(
+        architecture.platform(), 'default_os', 'default_target')
+
     if args.platform:
-        print(architecture.platform())
+        print(arch.platform)
+    elif args.operating_system:
+        print(arch.platform_os)
+    elif args.target:
+        print(arch.target)
     else:
-        print(architecture.sys_type())
+        print(arch)

lib/spack/spack/cmd/help.py

@@ -59,9 +59,9 @@
       @B{variant=value1,value2,value3}  set multi-value <variant> values
 
     architecture variants:
-      @m{target=target}                 specific <target> processor
-      @m{os=operating_system}           specific <operating_system>
       @m{platform=platform}             linux, darwin, cray, bgq, etc.
+      @m{os=operating_system}           specific <operating_system>
+      @m{target=target}                 specific <target> processor
       @m{arch=platform-os-target}       shortcut for all three above
 
     cross-compiling:

lib/spack/spack/test/cmd/arch.py

@@ -29,6 +29,27 @@
 
 
 def test_arch():
-    """Sanity check the arch command to make sure it works."""
+    """Sanity check ``spack arch`` to make sure it works."""
 
     arch()
+
+
+def test_arch_platform():
+    """Sanity check ``spack arch --platform`` to make sure it works."""
+
+    arch('-p')
+    arch('--platform')
+
+
+def test_arch_operating_system():
+    """Sanity check ``spack arch --operating-system`` to make sure it works."""
+
+    arch('-o')
+    arch('--operating-system')
+
+
+def test_arch_target():
+    """Sanity check ``spack arch --target`` to make sure it works."""
+
+    arch('-t')
+    arch('--target')