fix(summer): mask secret flag values in a delegate's error (WR-10)

cmd/summer/runtime.go

@@ -9,9 +9,9 @@ import (
 	"os/exec"
 	"os/signal"
 	"path/filepath"
-	"strings"
 	"syscall"
 
+	"git.golem15.com/golem15/summercms/internal/argmask"
 	"git.golem15.com/golem15/summercms/internal/build"
 	"git.golem15.com/golem15/summercms/internal/dev"
 	"git.golem15.com/golem15/summercms/modules/bonfire"
@@ -161,13 +161,17 @@ func appStreams(out bonfire.Output, terminal bool) (stdout, stderr io.Writer) {
 
 // runAppCmd runs cmd, the app binary started with argv, forwarding SIGINT
 // and SIGTERM to it. When the binary exits with a code, the error carries
-// that code (bonfire.WithExitCode) and is marked as already reported.
+// that code (bonfire.WithExitCode) and is marked as already reported. The
+// error names the command through argmask.Join, with the values of
+// secret-looking flags masked, on every branch: a binary that fails to
+// start or is ended by a signal gets summer's error block, and a signal
+// death keeps exit code 1.
 func runAppCmd(cmd *exec.Cmd, argv []string) error {
 	sigs := make(chan os.Signal, 2)
 	signal.Notify(sigs, os.Interrupt, syscall.SIGTERM)
 	defer signal.Stop(sigs)
 	if err := runChild(cmd, sigs); err != nil {
-		err = fmt.Errorf("summer: %s: %w", strings.Join(argv, " "), err)
+		err = fmt.Errorf("summer: %s: %w", argmask.Join(argv), err)
 		var exit *exec.ExitError
 		if errors.As(err, &exit) && exit.Exited() {
 			// The binary printed its own error; summer exits with its