cmd/link: remove alternate -X flag spelling

The Go 1.6 release notes say we'll remove the “-X name value” form
(in favor of the “-X name=value” form) in Go 1.7.
Do that.

Also establish the doc/go1.7.txt file.

Change-Id: Ie4565a6bc5dbcf155181754d8d92bfbb23c75338
Reviewed-on: https://go-review.googlesource.com/19614Reviewed-by: Ian Lance Taylor <iant@golang.org>

doc/go1.7.txt

+Tools:
+
+cmd/link: "-X name value" form gone (CL XXX)
+
+Ports:
+
+SOMETHING WILL HAPPEN
+
+API additions and behavior changes:
+
+SOMETHING WILL HAPPEN
+
+

src/cmd/go/go_test.go

@@ -1657,8 +1657,8 @@ func TestLdflagsArgumentsWithSpacesIssue3941(t *testing.T) {
 		func main() {
 			println(extern)
 		}`)
-	tg.run("run", "-ldflags", `-X main.extern "hello world"`, tg.path("main.go"))
-	tg.grepStderr("^hello world", `ldflags -X main.extern 'hello world' failed`)
+	tg.run("run", "-ldflags", `-X "main.extern=hello world"`, tg.path("main.go"))
+	tg.grepStderr("^hello world", `ldflags -X "main.extern=hello world"' failed`)
 }
 
 func TestGoTestCpuprofileLeavesBinaryBehind(t *testing.T) {

src/cmd/link/internal/ld/pobj.go

@@ -119,33 +119,6 @@ func Ldmain() {
 	obj.Flagstr("memprofile", "write memory profile to `file`", &memprofile)
 	obj.Flagint64("memprofilerate", "set runtime.MemProfileRate to `rate`", &memprofilerate)
 
-	// Clumsy hack to preserve old two-argument -X name val syntax for old scripts.
-	// Rewrite that syntax into new syntax -X name=val.
-	// TODO(rsc): Delete this hack in Go 1.6 or later.
-	var args []string
-	for i := 0; i < len(os.Args); i++ {
-		arg := os.Args[i]
-		if (arg == "-X" || arg == "--X") && i+2 < len(os.Args) && !strings.Contains(os.Args[i+1], "=") {
-			fmt.Fprintf(os.Stderr, "link: warning: option %s %s %s may not work in future releases; use %s %s=%s\n",
-				arg, os.Args[i+1], os.Args[i+2],
-				arg, os.Args[i+1], os.Args[i+2])
-			args = append(args, arg)
-			args = append(args, os.Args[i+1]+"="+os.Args[i+2])
-			i += 2
-			continue
-		}
-		if (strings.HasPrefix(arg, "-X=") || strings.HasPrefix(arg, "--X=")) && i+1 < len(os.Args) && strings.Count(arg, "=") == 1 {
-			fmt.Fprintf(os.Stderr, "link: warning: option %s %s may not work in future releases; use %s=%s\n",
-				arg, os.Args[i+1],
-				arg, os.Args[i+1])
-			args = append(args, arg+"="+os.Args[i+1])
-			i++
-			continue
-		}
-		args = append(args, arg)
-	}
-	os.Args = args
-
 	obj.Flagparse(usage)
 
 	startProfile()

test/linkx_run.go

@@ -18,7 +18,7 @@ import (
 )
 
 func main() {
-	test(" ") // old deprecated syntax
+	// test(" ") // old deprecated & removed syntax
 	test("=") // new syntax
 }