fix(cmd spec -y): add yaml doc separators (---)

lib/spack/spack/cmd/spec.py

@@ -108,11 +108,16 @@ 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))