introduce site overlays

site overlays are place in sysconfdir/overlays and take
precedence over distribution overlays with the same name.

Every `wwctl overlay` command changing overlays will create
an site overlay. distribution overlays can't be deleted or
modified with wwctl.

Signed-off-by: Christian Goll <cgoll@suse.com>

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

@@ -30,16 +30,20 @@ const initialTemplate = `# This is a Warewulf Template file.
 # Keep the following for better reference:
 # ---
 # This file is autogenerated by warewulf
-# Host:   {{.BuildHost}}
-# Time:   {{.BuildTime}}
-# Source: {{.BuildSource}}
 `
 
-func CobraRunE(cmd *cobra.Command, args []string) error {
+func CobraRunE(cmd *cobra.Command, args []string) (err error) {
 	overlayName := args[0]
 	fileName := args[1]
-
-	overlaySourceDir := overlay.OverlaySourceDir(overlayName)
+	createdSite := false
+	overlaySourceDir, isSite := overlay.OverlaySourceDir(overlayName)
+	if !isSite {
+		err = overlay.CreateSiteOverlay(overlayName)
+		if err != nil {
+			return err
+		}
+		createdSite = true
+	}
 	if !util.IsDir(overlaySourceDir) {
 		return fmt.Errorf("overlay does not exist: %s", overlayName)
 	}
@@ -102,12 +106,15 @@ func CobraRunE(cmd *cobra.Command, args []string) error {
 	} else {
 		if startTime == fileInfo.ModTime() {
 			wwlog.Debug("No change detected. Not updating overlay.")
-			os.Exit(0)
+			if createdSite {
+				os.Remove(overlaySourceDir)
+			}
+			return nil
 		}
 	}
 
 	// try renaming the tempfile to overlayfile first
-	err := os.Rename(tempFile.Name(), overlayFile)
+	err = os.Rename(tempFile.Name(), overlayFile)
 	if err != nil {
 		// if it fails, which probably means that they exists on different partitions
 		// fallback to data copy