Prepare for fetch cache

This probably needs to go upstream… not sure if I already did something about it.

(The document separator definitely needs lots of testing to be upstreamable. We could also try to use a parser that can handle the somewhat "illegally" formatted output.)

lib/spack/spack/cmd/spec.py

@@ -70,6 +70,12 @@ def setup_parser(subparser):
     subparser.add_argument(
         "-t", "--types", action="store_true", default=False, help="show dependency types"
     )
+    subparser.add_argument(
+        "--test",
+        default=None,
+        choices=["root", "all"],
+        help="concretize with test dependencies of only root packages or all packages",
+    )
     arguments.add_common_arguments(subparser, ["specs"])
     arguments.add_concretizer_args(subparser)
 
@@ -98,9 +104,17 @@ def spec(parser, args):
     # Use command line specified specs, otherwise try to use environment specs.
     if args.specs:
         input_specs = spack.cmd.parse_specs(args.specs)
-        concretized_specs = spack.cmd.parse_specs(args.specs, concretize=True)
+        if args.test == "all":
+            tests = True
+        elif args.test == "root":
+            tests = [spec.name for spec in input_specs]
+        else:
+            tests = False
+        concretized_specs = spack.cmd.parse_specs(args.specs, concretize=True, tests=tests)
         specs = list(zip(input_specs, concretized_specs))
     else:
+        if args.test is not None:
+            tty.die("spack spec for environments does not support test dependency selection")
         env = ev.active_environment()
         if env:
             env.concretize()
@@ -108,11 +122,16 @@ def spec(parser, args):
         else:
             tty.die("spack spec requires at least one spec or an active environment")
 
+    first_doc = True
     for input, output in specs:
         # With -y, just print YAML to output.
         if args.format:
             if args.format == "yaml":
                 # use write because to_yaml already has a newline.
+                if first_doc:
+                    first_doc = False
+                else:
+                    sys.stdout.write("---\n")
                 sys.stdout.write(output.to_yaml(hash=ht.dag_hash))
             elif args.format == "json":
                 print(output.to_json(hash=ht.dag_hash))