diff -u -r ./go11.go /Users/rsc/src/golang.org/x/vgo/vendor/cmd/go/go11.go
--- ./go11.go	2018-05-30 20:46:08.000000000 -0400
+++ /Users/rsc/src/golang.org/x/vgo/vendor/cmd/go/go11.go	2018-02-20 12:11:43.000000000 -0500
@@ -4,7 +4,7 @@

 // +build go1.1

-package main
+package Main

 // Test that go1.1 tag above is included in builds. main.go refers to this definition.
 const go11tag = true
diff -u -r ./go_test.go /Users/rsc/src/golang.org/x/vgo/vendor/cmd/go/go_test.go
--- ./go_test.go	2018-07-12 00:17:57.000000000 -0400
+++ /Users/rsc/src/golang.org/x/vgo/vendor/cmd/go/go_test.go	2018-07-12 00:09:46.000000000 -0400
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.

-package main_test
+package Main_test

 import (
 	"bytes"
@@ -120,2 +120,2 @@
 		testGo = filepath.Join(testTmpDir, "testgo"+exeSuffix)
-		args := []string{"build", "-tags", "testgo", "-o", testGo}
+		args := []string{"build", "-tags", "testgo", "-o", testGo, "../../.."}
@@ -867,7 +870,9 @@
 	tg.grepBoth("FAIL.*badtest/badvar", "test did not run everything")
 }

 func TestNewReleaseRebuildsStalePackagesInGOPATH(t *testing.T) {
+	t.Skip("vgo")
+
 	if testing.Short() {
 		t.Skip("don't rebuild the standard library in short mode")
 	}
@@ -1342,6 +1389,8 @@
 }

 func TestMoveHG(t *testing.T) {
+	t.Skip("vgo") // Failing in main branch too: non-hermetic hg configuration?
+
 	testMove(t, "hg", "vcs-test.golang.org/go/custom-hg-hello", "custom-hg-hello", "vcs-test.golang.org/go/custom-hg-hello/.hg/hgrc")
 }

@@ -1507,6 +1556,8 @@
 }

 func TestAccidentalGitCheckout(t *testing.T) {
+	t.Skip("vgo") // Failing in main branch too: https://golang.org/issue/22983
+
 	testenv.MustHaveExternalNetwork(t)
 	if _, err := exec.LookPath("git"); err != nil {
 		t.Skip("skipping because git binary not found")
@@ -2114,6 +2165,8 @@
 }

 func TestDefaultGOPATH(t *testing.T) {
+	t.Skip("vgo") // Needs a more realistic GOROOT; see RuntimeGoroot below.
+
 	tg := testgo(t)
 	defer tg.cleanup()
 	tg.parallel()
@@ -2172,6 +2225,8 @@
 // Issue 4186. go get cannot be used to download packages to $GOROOT.
 // Test that without GOPATH set, go get should fail.
 func TestGoGetIntoGOROOT(t *testing.T) {
+	t.Skip("vgo")
+
 	testenv.MustHaveExternalNetwork(t)

 	tg := testgo(t)
@@ -2771,6 +2771,8 @@ func TestTestBuildFailureOutput(t *testing.T) {
 }

 func TestCoverageFunc(t *testing.T) {
+	t.Skip("vgo")
+
 	tooSlow(t)
 	tg := testgo(t)
 	defer tg.cleanup()
@@ -3395,6 +3450,8 @@
 }

 func TestGoVetWithExternalTests(t *testing.T) {
+	t.Skip("vgo")
+
 	tg := testgo(t)
 	defer tg.cleanup()
 	tg.makeTempdir()
@@ -3404,6 +3461,8 @@
 }

 func TestGoVetWithTags(t *testing.T) {
+	t.Skip("vgo")
+
 	tg := testgo(t)
 	defer tg.cleanup()
 	tg.makeTempdir()
@@ -3413,6 +3472,8 @@
 }

 func TestGoVetWithFlagsOn(t *testing.T) {
+	t.Skip("vgo")
+
 	tg := testgo(t)
 	defer tg.cleanup()
 	tg.makeTempdir()
@@ -4754,6 +4815,8 @@
 }

 func TestExecutableGOROOT(t *testing.T) {
+	t.Skip("vgo")
+
 	skipIfGccgo(t, "gccgo has no GOROOT")
 	if runtime.GOOS == "openbsd" {
 		t.Skipf("test case does not work on %s, missing os.Executable", runtime.GOOS)
@@ -4829,6 +4892,8 @@
 	// Binaries built in the new tree should report the
 	// new tree when they call runtime.GOROOT.
 	t.Run("RuntimeGoroot", func(t *testing.T) {
+		t.Skip("vgo") // Needs "new/api" in GOROOT.
+
 		// Build a working GOROOT the easy way, with symlinks.
 		testenv.MustHaveSymlink(t)
 		if err := os.Symlink(filepath.Join(testGOROOT, "src"), tg.path("new/src")); err != nil {
@@ -4984,6 +5049,8 @@
 }

 func TestTestRegexps(t *testing.T) {
+	t.Skip("vgo") // fails with Go 1.10 testing package
+
 	tg := testgo(t)
 	defer tg.cleanup()
 	tg.setenv("GOPATH", filepath.Join(tg.pwd(), "testdata"))
@@ -5119,6 +5186,8 @@
 }

 func TestExecBuildX(t *testing.T) {
+	t.Skip("vgo")
+
 	tooSlow(t)
 	if !canCgo {
 		t.Skip("skipping because cgo not enabled")
@@ -5761,6 +5830,8 @@
 }

 func TestTestVet(t *testing.T) {
+	t.Skip("vgo")
+
 	tooSlow(t)
 	tg := testgo(t)
 	defer tg.cleanup()
@@ -5945,6 +6011,8 @@
 }

 func TestGoTestJSON(t *testing.T) {
+	t.Skip("vgo") // "did not see skip"
+
 	skipIfGccgo(t, "gccgo does not have standard packages")
 	tooSlow(t)

@@ -5983,6 +6051,8 @@
 }

 func TestFailFast(t *testing.T) {
+	t.Skip("vgo") // fails with Go 1.10 testing package
+
 	tooSlow(t)
 	tg := testgo(t)
 	defer tg.cleanup()
diff -u -r ./go_unix_test.go /Users/rsc/src/golang.org/x/vgo/vendor/cmd/go/go_unix_test.go
--- ./go_unix_test.go	2018-06-04 09:24:18.000000000 -0400
+++ /Users/rsc/src/golang.org/x/vgo/vendor/cmd/go/go_unix_test.go	2018-02-20 12:11:43.000000000 -0500
@@ -4,6 +4,6 @@

 // +build darwin dragonfly freebsd linux netbsd openbsd solaris

-package main_test
+package Main_test

 import (
diff -u -r ./go_windows_test.go /Users/rsc/src/golang.org/x/vgo/vendor/cmd/go/go_windows_test.go
--- ./go_windows_test.go	2018-06-04 09:24:18.000000000 -0400
+++ /Users/rsc/src/golang.org/x/vgo/vendor/cmd/go/go_windows_test.go	2018-02-20 12:11:43.000000000 -0500
@@ -2,6 +2,6 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.

-package main
+package Main

 import (
diff -u -r ./script_test.go /Users/rsc/src/golang.org/x/vgo/vendor/cmd/go/script_test.go
--- ./script_test.go	2018-06-04 09:24:18.000000000 -0400
+++ /Users/rsc/src/golang.org/x/vgo/vendor/cmd/go/script_test.go	2018-02-20 12:11:43.000000000 -0500
@@ -5,6 +5,6 @@
 // Script-driven tests.
 // See testdata/script/README for an overview.

-package main_test
+package Main_test

 import (
diff -u -r ./internal/base/base.go /Users/rsc/src/golang.org/x/vgo/vendor/cmd/go/internal/base/base.go
--- ./internal/base/base.go	2018-06-04 09:24:18.000000000 -0400
+++ /Users/rsc/src/golang.org/x/vgo/vendor/cmd/go/internal/base/base.go	2018-02-23 16:13:50.000000000 -0500
@@ -15,6 +15,7 @@
 	"log"
 	"os"
 	"os/exec"
+	"runtime/debug"
 	"strings"
 	"sync"

@@ -86,13 +87,20 @@
 	os.Exit(exitStatus)
 }

+var et = flag.Bool("et", false, "print stack traces with errors")
+
 func Fatalf(format string, args ...interface{}) {
 	Errorf(format, args...)
 	Exit()
 }

 func Errorf(format string, args ...interface{}) {
-	log.Printf(format, args...)
+	if *et {
+		stack := debug.Stack()
+		log.Printf("%s\n%s", fmt.Sprintf(format, args...), stack)
+	} else {
+		log.Printf(format, args...)
+	}
 	SetExitStatus(1)
 }

diff -u -r ./internal/cfg/cfg.go /Users/rsc/src/golang.org/x/vgo/vendor/cmd/go/internal/cfg/cfg.go
--- ./internal/cfg/cfg.go	2018-07-12 00:17:57.000000000 -0400
+++ /Users/rsc/src/golang.org/x/vgo/vendor/cmd/go/internal/cfg/cfg.go	2018-07-12 00:03:05.000000000 -0400
@@ -7,13 +7,14 @@
 package cfg

 import (
+	"bytes"
 	"fmt"
 	"go/build"
+	"io/ioutil"
+	"log"
 	"os"
 	"path/filepath"
 	"runtime"
-
-	"cmd/internal/objabi"
 )

 // These are general "build flags" used by build and other commands.
@@ -90,10 +91,10 @@
 	GOROOT_FINAL = findGOROOT_FINAL()

 	// Used in envcmd.MkEnv and build ID computations.
-	GOARM    = fmt.Sprint(objabi.GOARM)
-	GO386    = objabi.GO386
-	GOMIPS   = objabi.GOMIPS
-	GOMIPS64 = objabi.GOMIPS64
+	GOARM, GO386, GOMIPS, GOMIPS64 = objabi()
+
+	// C and C++ compilers
+	CC, CXX = compilers()
 )

 // Update build context to use our computed GOROOT.
@@ -109,18 +110,75 @@
 	}
 }

-// There is a copy of findGOROOT, isSameDir, and isGOROOT in
-// x/tools/cmd/godoc/goroot.go.
-// Try to keep them in sync for now.
-
-// findGOROOT returns the GOROOT value, using either an explicitly
-// provided environment variable, a GOROOT that contains the current
-// os.Executable value, or else the GOROOT that the binary was built
-// with from runtime.GOROOT().
-//
-// There is a copy of this code in x/tools/cmd/godoc/goroot.go.
+func objabi() (GOARM, GO386, GOMIPS, GOMIPS64 string) {
+	data, err := ioutil.ReadFile(filepath.Join(GOROOT, "src/cmd/internal/objabi/zbootstrap.go"))
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "go objabi: %v\n", err)
+	}
+
+	find := func(key string) string {
+		if env := os.Getenv(key); env != "" {
+			return env
+		}
+		i := bytes.Index(data, []byte("default"+key+" = `"))
+		if i < 0 {
+			if key == "GOMIPS64" { // new in Go 1.11
+				return ""
+			}
+			fmt.Fprintf(os.Stderr, "go objabi: cannot find %s\n", key)
+			os.Exit(2)
+		}
+		line := data[i:]
+		line = line[bytes.IndexByte(line, '`')+1:]
+		return string(line[:bytes.IndexByte(line, '`')])
+	}
+
+	return find("GOARM"), find("GO386"), find("GOMIPS"), find("GOMIPS64")
+}
+
+func compilers() (CC, CXX string) {
+	data, err := ioutil.ReadFile(filepath.Join(GOROOT, "src/cmd/go/internal/cfg/zdefaultcc.go"))
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "go compilers: %v\n", err)
+	}
+
+	find := func(key string) string {
+		if env := os.Getenv(key); env != "" {
+			return env
+		}
+		fi := bytes.Index(data, []byte("Default"+key+"(goos, goarch string)"))
+		if fi < 0 {
+			fmt.Fprintf(os.Stderr, "go compilers: cannot find %s\n", key)
+			os.Exit(2)
+		}
+		i := bytes.Index(data[fi:], []byte("\treturn "))
+		if i < 0 {
+			fmt.Fprintf(os.Stderr, "go compilers: cannot find %s\n", key)
+			os.Exit(2)
+		}
+		line := data[fi+i:]
+		line = line[bytes.IndexByte(line, '"')+1:]
+		return string(line[:bytes.IndexByte(line, '"')])
+	}
+
+	return find("CC"), find("CXX")
+}
+
 func findGOROOT() string {
+	goroot := findGOROOT1()
+	_, err := os.Stat(filepath.Join(goroot, "api/go1.10.txt"))
+	if err != nil {
+		log.SetFlags(0)
+		log.Fatalf("go requires Go 1.10 but VGOROOT=%s is not a Go 1.10 source tree", goroot)
+	}
+	return goroot
+}
+
+func findGOROOT1() string {
+	if env := os.Getenv("VGOROOT"); env != "" {
+		return filepath.Clean(env)
+	}
 	if env := os.Getenv("GOROOT"); env != "" {
 		return filepath.Clean(env)
 	}
 	def := filepath.Clean(runtime.GOROOT())
diff -u -r ./internal/help/help.go /Users/rsc/src/golang.org/x/vgo/vendor/cmd/go/internal/help/help.go
--- ./internal/help/help.go	2018-07-12 00:17:57.000000000 -0400
+++ /Users/rsc/src/golang.org/x/vgo/vendor/cmd/go/internal/help/help.go	2018-07-12 00:03:05.000000000 -0400
@@ -72,6 +72,10 @@

 var usageTemplate = `Go is a tool for managing Go source code.

+This is vgo, an experimental go command with support for package versioning.
+Even though you are invoking it as vgo, most of the messages printed will
+still say "go", not "vgo". Sorry.
+
 Usage:

 	go command [arguments]
diff -u -r ./internal/version/version.go /Users/rsc/src/golang.org/x/vgo/vendor/cmd/go/internal/version/version.go
--- ./internal/version/version.go	2018-06-04 09:24:18.000000000 -0400
+++ /Users/rsc/src/golang.org/x/vgo/vendor/cmd/go/internal/version/version.go	2018-07-10 16:04:55.000000000 -0400
@@ -10,8 +10,9 @@
 	"runtime"

 	"cmd/go/internal/base"
+	"cmd/go/internal/work"
 )

 var CmdVersion = &base.Command{
 	Run:       runVersion,
 	UsageLine: "version",
@@ -24,5 +27,5 @@
 		cmd.Usage()
 	}

-	fmt.Printf("go version %s %s/%s\n", runtime.Version(), runtime.GOOS, runtime.GOARCH)
+	fmt.Printf("go version %s %s/%s vgo:%s\n", work.RuntimeVersion, runtime.GOOS, runtime.GOARCH, version)
 }
diff -u -r ./internal/work/build.go /Users/rsc/src/golang.org/x/vgo/vendor/cmd/go/internal/work/build.go
--- ./internal/work/build.go	2018-07-12 00:17:57.000000000 -0400
+++ /Users/rsc/src/golang.org/x/vgo/vendor/cmd/go/internal/work/build.go	2018-07-10 17:04:18.000000000 -0400
@@ -5,9 +5,11 @@
 package work

 import (
+	"bytes"
 	"errors"
 	"fmt"
 	"go/build"
+	"io/ioutil"
 	"os"
 	"os/exec"
 	"path"
@@ -274,7 +276,25 @@

 var pkgsFilter = func(pkgs []*load.Package) []*load.Package { return pkgs }

-var runtimeVersion = runtime.Version()
+var runtimeVersion = getRuntimeVersion()
+var RuntimeVersion = runtimeVersion
+
+func getRuntimeVersion() string {
+	data, err := ioutil.ReadFile(filepath.Join(cfg.GOROOT, "src/runtime/internal/sys/zversion.go"))
+	if err != nil {
+		base.Fatalf("go: %v", err)
+	}
+	i := bytes.Index(data, []byte("TheVersion = `"))
+	if i < 0 {
+		base.Fatalf("go: cannot find TheVersion")
+	}
+	data = data[i+len("TheVersion = `"):]
+	j := bytes.IndexByte(data, '`')
+	if j < 0 {
+		base.Fatalf("go: cannot find TheVersion")
+	}
+	return string(data[:j])
+}

 func runBuild(cmd *base.Command, args []string) {
 	BuildInit()
diff -u -r ./internal/work/buildid.go /Users/rsc/src/golang.org/x/vgo/vendor/cmd/go/internal/work/buildid.go
--- ./internal/work/buildid.go	2018-07-06 16:52:53.000000000 -0400
+++ /Users/rsc/src/golang.org/x/vgo/vendor/cmd/go/internal/work/buildid.go	2018-06-27 21:01:27.000000000 -0400
@@ -134,6 +134,8 @@
 	return string(dst[:])
 }

+var oldVet = false
+
 // toolID returns the unique ID to use for the current copy of the
 // named tool (asm, compile, cover, link).
 //
@@ -166,6 +168,10 @@
 // build setups agree on details like $GOROOT and file name paths, but at least the
 // tool IDs do not make it impossible.)
 func (b *Builder) toolID(name string) string {
+	if name == "vet" && oldVet {
+		return ""
+	}
+
 	b.id.Lock()
 	id := b.toolIDCache[name]
 	b.id.Unlock()
@@ -190,6 +196,10 @@
 	cmd.Stdout = &stdout
 	cmd.Stderr = &stderr
 	if err := cmd.Run(); err != nil {
+		if name == "vet" {
+			oldVet = true
+			return ""
+		}
 		base.Fatalf("%s: %v\n%s%s", desc, err, stdout.Bytes(), stderr.Bytes())
 	}

diff -u -r ./internal/work/exec.go /Users/rsc/src/golang.org/x/vgo/vendor/cmd/go/internal/work/exec.go
--- ./internal/work/exec.go	2018-07-12 00:17:57.000000000 -0400
+++ /Users/rsc/src/golang.org/x/vgo/vendor/cmd/go/internal/work/exec.go	2018-07-12 00:03:05.000000000 -0400
@@ -972,7 +972,7 @@
 	// TODO(rsc,gri): Try to remove this for Go 1.11.
 	//
 	// Disabled 2018-04-20. Let's see if we can do without it.
-	// vcfg.SucceedOnTypecheckFailure = cfg.CmdName == "test"
+	vcfg.SucceedOnTypecheckFailure = cfg.CmdName == "test"

 	js, err := json.MarshalIndent(vcfg, "", "\t")
 	if err != nil {
diff -u -r ./internal/work/gc.go /Users/rsc/src/golang.org/x/vgo/vendor/cmd/go/internal/work/gc.go
--- ./internal/work/gc.go	2018-07-06 16:52:53.000000000 -0400
+++ /Users/rsc/src/golang.org/x/vgo/vendor/cmd/go/internal/work/gc.go	2018-06-27 21:01:27.000000000 -0400
@@ -20,7 +20,6 @@
 	"cmd/go/internal/cfg"
 	"cmd/go/internal/load"
 	"cmd/go/internal/str"
-	"cmd/internal/objabi"
 	"crypto/sha1"
 )

@@ -167,11 +166,6 @@
 		}
 	}

-	// TODO: Test and delete these conditions.
-	if objabi.Fieldtrack_enabled != 0 || objabi.Preemptibleloops_enabled != 0 || objabi.Clobberdead_enabled != 0 {
-		canDashC = false
-	}
-
 	if !canDashC {
 		return 1
 	}
diff -u -r ./main.go /Users/rsc/src/golang.org/x/vgo/vendor/cmd/go/main.go
--- ./main.go	2018-07-12 00:17:57.000000000 -0400
+++ /Users/rsc/src/golang.org/x/vgo/vendor/cmd/go/main.go	2018-07-10 16:04:55.000000000 -0400
@@ -4,7 +4,7 @@

 //go:generate ./mkalldocs.sh

-package main
+package Main

 import (
 	"flag"
@@ -74,7 +74,7 @@
 	}
 }

-func main() {
+func Main() {
 	_ = go11tag
 	flag.Usage = base.Usage
 	flag.Parse()
diff -u -r ./note_test.go /Users/rsc/src/golang.org/x/vgo/vendor/cmd/go/note_test.go
--- ./note_test.go	2018-07-12 00:14:08.000000000 -0400
+++ /Users/rsc/src/golang.org/x/vgo/vendor/cmd/go/note_test.go	2018-07-11 23:25:10.000000000 -0400
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.

-package main_test
+package Main_test

 import (
 	"bytes"
diff -u -r ./proxy_test.go /Users/rsc/src/golang.org/x/vgo/vendor/cmd/go/proxy_test.go
--- ./proxy_test.go	2018-07-12 00:14:08.000000000 -0400
+++ /Users/rsc/src/golang.org/x/vgo/vendor/cmd/go/proxy_test.go	2018-07-11 23:25:10.000000000 -0400
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.

-package main_test
+package Main_test

 import (
 	"bytes"
diff -u -r ./vendor_test.go /Users/rsc/src/golang.org/x/vgo/vendor/cmd/go/vendor_test.go
--- ./vendor_test.go	2018-07-12 00:14:08.000000000 -0400
+++ /Users/rsc/src/golang.org/x/vgo/vendor/cmd/go/vendor_test.go	2018-07-11 23:25:10.000000000 -0400
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.

-package main_test
+package Main_test

 import (
 	"bytes"