cmd/go: version command should error when given bad args

For example, 'go version -m' happily gives you Go's own version, even
though the -m flag only makes sense when grabbing the version of a
binary on disk.

Similarly, if any of the directly named files can't be found, the tool
would succeed. That's acceptable if an error is encountered while
walking a large directory, but not when locating a path directly given
by the user.

These added test cases run even in short mode, as 'go build' is not
needed for them.

Change-Id: I7bb40b72853799e31d9f86cc5e999c8d57813eef
Reviewed-on: https://go-review.googlesource.com/c/go/+/221397
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Bryan C. Mills <bcmills@google.com>

src/cmd/go/internal/version/version.go

@@ -53,6 +53,11 @@ var (
 
 func runVersion(cmd *base.Command, args []string) {
 	if len(args) == 0 {
+		if *versionM || *versionV {
+			fmt.Fprintf(os.Stderr, "go version: flags can only be used with arguments\n")
+			base.SetExitStatus(2)
+			return
+		}
 		fmt.Printf("go version %s %s/%s\n", runtime.Version(), runtime.GOOS, runtime.GOARCH)
 		return
 	}
@@ -61,6 +66,7 @@ func runVersion(cmd *base.Command, args []string) {
 		info, err := os.Stat(arg)
 		if err != nil {
 			fmt.Fprintf(os.Stderr, "%v\n", err)
+			base.SetExitStatus(1)
 			continue
 		}
 		if info.IsDir() {

src/cmd/go/testdata/script/version.txt

@@ -1,4 +1,16 @@
+# Without arguments, we just print Go's own version.
+go version
+stdout '^go version'
+
+# Flags without files, or paths to misisng files, should error.
+! go version missing.exe
+! go version -m
+stderr 'with arguments'
+! go version -v
+stderr 'with arguments'
+
 env GO111MODULE=on
+# Skip the builds below if we are running in short mode.
 [short] skip
 
 # Check that 'go version' and 'go version -m' work on a binary built in module mode.