cmd/go: final edits for add go list -cgo and -export

These got lost because I violated the cardinal rule of Gerrit
which is never click the Submit button in the web UI.

Change-Id: I8ccdfb5d8691960f244941036d33fb5a5a3f0c9a
Reviewed-on: https://go-review.googlesource.com/117015Reviewed-by: Russ Cox <rsc@golang.org>

src/cmd/go/alldocs.go

@@ -579,7 +579,7 @@
 //
 // Usage:
 //
-// 	go list [-cgo] [-deps] [-e] [-f format] [-json] [-list] [-test] [build flags] [packages]
+// 	go list [-cgo] [-deps] [-e] [-export] [-f format] [-json] [-list] [-test] [build flags] [packages]
 //
 // List lists the packages named by the import paths, one per line.
 //
@@ -706,9 +706,8 @@
 // a non-nil Error field; other information may or may not be missing
 // (zeroed).
 //
-// The -export flag causes list to set the package's Export field to
-// the name of a file containing up-to-date export information for
-// the given package.
+// The -export flag causes list to set the Export field to the name of a
+// file containing up-to-date export information for the given package.
 //
 // The -test flag causes list to report not only the named packages
 // but also their test binaries (for packages with tests), to convey to

src/cmd/go/internal/list/list.go

@@ -23,7 +23,7 @@ import (
 )
 
 var CmdList = &base.Command{
-	UsageLine: "list [-cgo] [-deps] [-e] [-f format] [-json] [-list] [-test] [build flags] [packages]",
+	UsageLine: "list [-cgo] [-deps] [-e] [-export] [-f format] [-json] [-list] [-test] [build flags] [packages]",
 	Short:     "list packages",
 	Long: `
 List lists the packages named by the import paths, one per line.
@@ -151,9 +151,8 @@ printing. Erroneous packages will have a non-empty ImportPath and
 a non-nil Error field; other information may or may not be missing
 (zeroed).
 
-The -export flag causes list to set the package's Export field to
-the name of a file containing up-to-date export information for
-the given package.
+The -export flag causes list to set the Export field to the name of a
+file containing up-to-date export information for the given package.
 
 The -test flag causes list to report not only the named packages
 but also their test binaries (for packages with tests), to convey to