Fleshed out the framework of most of the wwctl overlay command group.

internal/app/wwctl/overlay/build/main.go

@@ -0,0 +1,58 @@
+package build
+
+import (
+	"github.com/hpcng/warewulf/internal/pkg/assets"
+	"github.com/hpcng/warewulf/internal/pkg/overlay"
+	"github.com/hpcng/warewulf/internal/pkg/wwlog"
+	"github.com/spf13/cobra"
+	"os"
+)
+
+func CobraRunE(cmd *cobra.Command, args []string) error {
+
+
+	var updateNodes []assets.NodeInfo
+
+	if len(args) > 0 && BuildAll == false {
+		nodes, err := assets.FindAllNodes()
+		if err != nil {
+			wwlog.Printf(wwlog.ERROR, "Cloud not get nodeList: %s\n", err)
+			os.Exit(1)
+		}
+
+		for _, node := range nodes {
+			if SystemOverlay == true && node.SystemOverlay == args[0] {
+				updateNodes = append(updateNodes, node)
+			} else if node.RuntimeOverlay == args[0] {
+				updateNodes = append(updateNodes, node)
+			}
+		}
+	} else {
+		var err error
+		updateNodes, err = assets.FindAllNodes()
+		if err != nil {
+			wwlog.Printf(wwlog.ERROR, "Cloud not get nodeList: %s\n", err)
+			os.Exit(1)
+		}
+	}
+
+	wwlog.Printf(wwlog.DEBUG, "Checking on system overlay update\n")
+	if SystemOverlay == true || BuildAll == true {
+		wwlog.Printf(wwlog.INFO, "Updating System Overlays...\n")
+		err := overlay.SystemBuild(updateNodes, true)
+		if err != nil {
+			wwlog.Printf(wwlog.WARN, "Some system overlays failed to be generated\n")
+		}
+	}
+
+	wwlog.Printf(wwlog.DEBUG, "Checking on system overlay update\n")
+	if SystemOverlay == false || BuildAll == true {
+		wwlog.Printf(wwlog.INFO, "Updating Runtime Overlays...\n")
+		err := overlay.RuntimeBuild(updateNodes, true)
+		if err != nil {
+			wwlog.Printf(wwlog.WARN, "Some runtime overlays failed to be generated\n")
+		}
+	}
+
+	return nil
+}