cmd/go: add a chmod command to script_test

Change-Id: I5d4f65553f6c368d101be59aae9440f5ec9573b7
Reviewed-on: https://go-review.googlesource.com/c/153461
Run-TryBot: Bryan C. Mills <bcmills@google.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/cmd/go/script_test.go

@@ -342,6 +342,7 @@ Script:
 var scriptCmds = map[string]func(*testScript, bool, []string){
 	"addcrlf": (*testScript).cmdAddcrlf,
 	"cd":      (*testScript).cmdCd,
+	"chmod":   (*testScript).cmdChmod,
 	"cmp":     (*testScript).cmdCmp,
 	"cmpenv":  (*testScript).cmdCmpenv,
 	"cp":      (*testScript).cmdCp,
@@ -400,6 +401,24 @@ func (ts *testScript) cmdCd(neg bool, args []string) {
 	fmt.Fprintf(&ts.log, "%s\n", ts.cd)
 }
 
+// chmod changes permissions for a file or directory.
+func (ts *testScript) cmdChmod(neg bool, args []string) {
+	if neg {
+		ts.fatalf("unsupported: ! chmod")
+	}
+	if len(args) < 2 {
+		ts.fatalf("usage: chmod perm paths...")
+	}
+	perm, err := strconv.ParseUint(args[0], 0, 32)
+	if err != nil || perm&uint64(os.ModePerm) != perm {
+		ts.fatalf("invalid mode: %s", args[0])
+	}
+	for _, path := range args[1:] {
+		err := os.Chmod(path, os.FileMode(perm))
+		ts.check(err)
+	}
+}
+
 // cmp compares two files.
 func (ts *testScript) cmdCmp(neg bool, args []string) {
 	if neg {

src/cmd/go/testdata/script/README

@@ -86,6 +86,10 @@ The commands are:
 - cd dir
   Change to the given directory for future commands.
 
+- chmod perm path...
+  Change the permissions of the files or directories named by the path arguments
+  to be equal to perm. Only numerical permissions are supported.
+
 - cmp file1 file2
   Check that the named files have the same content.
   By convention, file1 is the actual data and file2 the expected data.