vpython: Add primary execution package.

vpython/cipd/cipd_test.go

 // Copyright 2017 The LUCI Authors. All rights reserved.
 // Use of this source code is governed under the Apache License, Version 2.0
 // that can be found in the LICENSE file.
 
 package cipd
 
 import (
         "bytes"
         "testing"
 
@@ skipping 13 matching lines @@
                                 Path: "foo/bar",
                         }
                         So(validatePackage(pkg), ShouldNotBeNil)
                         So(func() {
                                 _ = writeEnsureFile(&buf, []*env.Spec_Package{pkg})
                         }, ShouldPanic)
                 })
 
                 Convey(`Can write a manifest for packages`, func() {
                         err := writeEnsureFile(&buf, []*env.Spec_Package{
-                                &env.Spec_Package{"foo/bar", "baz"},
-                                &env.Spec_Package{"pants", "key:value"},
+                                {"foo/bar", "baz"},
+                                {"pants", "key:value"},
                         })
                         So(err, ShouldBeNil)
                         So(buf.String(), ShouldResemble, "foo/bar baz\npants key:value\n")
                 })
         })
 }