cmd/go: warn on get from code.google.com that it is shutting down

Fixes #10193.

Change-Id: Ibbb747babb697a66b943e5da76b0ada41f1fb14f
Reviewed-on: https://go-review.googlesource.com/12070
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>

src/cmd/go/get.go

@@ -205,6 +205,16 @@ func download(arg string, parent *Package, stk *importStack, getTestDeps bool) {
 			return
 		}
 
+		// Warn that code.google.com is shutting down.  We
+		// issue the warning here because this is where we
+		// have the import stack.
+		if strings.HasPrefix(p.ImportPath, "code.google.com") {
+			fmt.Fprintf(os.Stderr, "warning: code.google.com is shutting down; import path %v will stop working\n", p.ImportPath)
+			if len(*stk) > 1 {
+				fmt.Fprintf(os.Stderr, "warning: package %v\n", strings.Join(*stk, "\n\timports "))
+			}
+		}
+
 		args := []string{arg}
 		// If the argument has a wildcard in it, re-evaluate the wildcard.
 		// We delay this until after reloadPackage so that the old entry

src/cmd/go/go_test.go

@@ -2019,3 +2019,15 @@ func TestGoGetInsecureCustomDomain(t *testing.T) {
 	tg.runFail("get", "-d", repo)
 	tg.run("get", "-d", "-insecure", repo)
 }
+
+func TestIssue10193(t *testing.T) {
+	testenv.MustHaveExternalNetwork(t)
+
+	tg := testgo(t)
+	defer tg.cleanup()
+	tg.parallel()
+	tg.tempDir("src")
+	tg.setenv("GOPATH", tg.path("."))
+	tg.runFail("get", "code.google.com/p/rsc-svn")
+	tg.grepStderr("is shutting down", "missed warning about code.google.com")
+}