Minor fixes to rpmtree command

(1) The error checking at the beginning isn't necessary because we also
    want to support WORKSPACE mode.

(2) If we pass the default configname through to AddTree() then we'll
    generate the WORKSPACE file as if we had a lock file, which is not
    what we desire

cmd/rpmtree.go

@@ -1,7 +1,7 @@
 package main
 
 import (
-	"errors"
+	"fmt"
 	"os"
 
 	"github.com/bazelbuild/buildtools/build"
@@ -137,10 +137,6 @@ func NewRpmTreeCmd() *cobra.Command {
 		Short: "Writes a rpmtree rule and its rpmdependencies to bazel files",
 		Args:  cobra.MinimumNArgs(1),
 		RunE: func(cmd *cobra.Command, required []string) error {
-			if rpmtreeopts.toMacro != "" && rpmtreeopts.lockfile != "" {
-				return errors.New("Must provide at most one of --lockfile --to-macro")
-			}
-
 			repos, err := repo.LoadRepoFiles(rpmtreeopts.repofiles)
 			if err != nil {
 				return err
@@ -173,9 +169,12 @@ func NewRpmTreeCmd() *cobra.Command {
 			}
 
 			var handler Handler
+			var configname string
+
 			if rpmtreeopts.toMacro != "" {
 				handler, err = NewMacroHandler(rpmtreeopts.toMacro)
 			} else if rpmtreeopts.lockfile != "" {
+				configname = rpmtreeopts.configname
 				handler, err = NewLockFileHandler(
 					rpmtreeopts.configname,
 					rpmtreeopts.lockfile,
@@ -198,7 +197,7 @@ func NewRpmTreeCmd() *cobra.Command {
 				return err
 			}
 
-			bazel.AddTree(rpmtreeopts.name, rpmtreeopts.configname, build, install, rpmtreeopts.arch, rpmtreeopts.public)
+			bazel.AddTree(rpmtreeopts.name, configname, build, install, rpmtreeopts.arch, rpmtreeopts.public)
 
 			handler.PruneRPMs(build)
 			logrus.Info("Writing bazel files.")