core: make rook version more readable

during pre-validation check, rook version was
printed in multiple lines with golang version
which was making it difficult to read. Now, it
prints in one single like with the golang version.

Signed-off-by: subhamkrai <srai@redhat.com>

cmd/commands/root.go

@@ -18,6 +18,7 @@ package command
 import (
 	"context"
 	"fmt"
+	"regexp"
 	"strings"
 
 	"github.com/rook/kubectl-rook-ceph/pkg/exec"
@@ -106,7 +107,11 @@ func PreValidationCheck(ctx context.Context, k8sclientset *k8sutil.Clientsets, o
 	}
 
 	rookVersion := exec.RunCommandInOperatorPod(ctx, k8sclientset, "rook", []string{"version"}, operatorNamespace, cephClusterNamespace, true, false)
+	re := regexp.MustCompile("(?m)[\r\n]+^.*go: go.*$") // remove the go version from the output
+	rookVersion = re.ReplaceAllString(rookVersion, "")
+	rookVersion = strings.TrimSpace(rookVersion) // remove any trailing newlines
 	if strings.Contains(rookVersion, "alpha") || strings.Contains(rookVersion, "beta") {
 		logging.Warning("rook version '%s' is running a pre-release version of Rook.", rookVersion)
+		fmt.Println()
 	}
 }