added the wwctl overlay parse command

The `wwctl overlay parse -n NODE FILE` will interpret the given overlay file and print it stdout, via wwlog.PRINTF.
The overlay code had to be refactored for this, but hopefully this makes the code a bit more readable. Also the tstruct has not its own initilization code.

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

@@ -0,0 +1,83 @@
+package parse
+
+import (
+	"bufio"
+	"bytes"
+	"os"
+	"path/filepath"
+	"regexp"
+
+	"github.com/hpcng/warewulf/internal/pkg/node"
+	"github.com/hpcng/warewulf/internal/pkg/overlay"
+	"github.com/hpcng/warewulf/internal/pkg/util"
+	"github.com/hpcng/warewulf/internal/pkg/wwlog"
+	"github.com/spf13/cobra"
+)
+
+func CobraRunE(cmd *cobra.Command, args []string) error {
+	var host node.NodeInfo
+	if NodeName == "" {
+		host.Kernel = new(node.KernelEntry)
+		host.Ipmi = new(node.IpmiEntry)
+		var idEntry node.Entry
+		hostname, _ := os.Hostname()
+		idEntry.Set(hostname)
+		host.Id = idEntry
+	} else {
+		nodeDB, err := node.New()
+		if err != nil {
+			wwlog.Printf(wwlog.ERROR, "Could not open node configuration: %s\n", err)
+			os.Exit(1)
+		}
+		nodes, err := nodeDB.FindAllNodes()
+		if err != nil {
+			wwlog.Printf(wwlog.ERROR, "Could not get node list: %s\n", err)
+			os.Exit(1)
+		}
+		node := node.FilterByName(nodes, []string{NodeName})
+		if len(node) != 1 {
+			wwlog.Printf(wwlog.ERROR, "%v does not identify a single node\n", NodeName)
+			os.Exit(1)
+		}
+		host = node[0]
+	}
+	if !util.IsFile(args[0]) {
+		wwlog.Printf(wwlog.ERROR, "%s is not a file\n", args[0])
+	}
+	tstruct := overlay.InitStruct(host)
+	buffer, backupFile, writeFile, err := overlay.RenderTemplateFile(args[0], tstruct)
+	if err != nil {
+		return err
+	}
+	if filepath.Ext(args[0]) != ".ww" {
+		wwlog.Printf(wwlog.WARN, "%s has not the '.ww' so wont be rendered if in overlay\n", args[0])
+	}
+	wwlog.Printf(wwlog.INFO, "backupFile: %v\nwriteFile: %v\n", backupFile, writeFile)
+	var outBuffer bytes.Buffer
+	// search for magic file name comment
+	bufferScanner := bufio.NewScanner(bytes.NewReader(buffer.Bytes()))
+	bufferScanner.Split(overlay.ScanLines)
+	reg := regexp.MustCompile(`.*{{\s*/\*\s*file\s*["'](.*)["']\s*\*/\s*}}.*`)
+	foundFileComment := false
+	destFileName := args[0]
+	for bufferScanner.Scan() {
+		line := bufferScanner.Text()
+		filenameFromTemplate := reg.FindAllStringSubmatch(line, -1)
+		if len(filenameFromTemplate) != 0 {
+			wwlog.Printf(wwlog.DEBUG, "Found multifile comment, new filename %s\n", filenameFromTemplate[0][1])
+			if foundFileComment {
+				wwlog.Printf(wwlog.INFO, "%s", outBuffer.String())
+				outBuffer.Reset()
+			}
+			destFileName = filenameFromTemplate[0][1]
+			wwlog.Printf(wwlog.INFO, "Filename: %s\n\n", destFileName)
+			wwlog.Printf(wwlog.INFO, "%s", outBuffer.String())
+			foundFileComment = true
+		} else {
+			_, _ = outBuffer.WriteString(line)
+		}
+	}
+	wwlog.Printf(wwlog.INFO, "Filename: %s\n\n", destFileName)
+	wwlog.Printf(wwlog.INFO, "%s", outBuffer.String())
+	return nil
+}

internal/app/wwctl/overlay/parse/root.go

@@ -0,0 +1,41 @@
+package parse
+
+import (
+	"log"
+
+	"github.com/hpcng/warewulf/internal/pkg/node"
+	"github.com/spf13/cobra"
+)
+
+var (
+	baseCmd = &cobra.Command{
+		DisableFlagsInUseLine: true,
+		Use:                   "parse [OPTIONS] FILE_NAME",
+		Short:                 "parses interprets the given file as warewulf template",
+		Long:                  "This command tries to parse a given file as warewulf template, it needs not to be in overlay folder.",
+		RunE:                  CobraRunE,
+		Aliases:               []string{"parse"},
+		Args:                  cobra.ExactArgs(1),
+	}
+	NodeName string
+)
+
+func init() {
+	baseCmd.PersistentFlags().StringVarP(&NodeName, "node", "n", "", "node used for the variables in the template")
+	if err := baseCmd.RegisterFlagCompletionFunc("node", func(cmd *cobra.Command, args []string, toComplete string) ([]string, cobra.ShellCompDirective) {
+		nodeDB, _ := node.New()
+		nodes, _ := nodeDB.FindAllNodes()
+		var node_names []string
+		for _, node := range nodes {
+			node_names = append(node_names, node.Id.Get())
+		}
+		return node_names, cobra.ShellCompDirectiveNoFileComp
+	}); err != nil {
+		log.Println(err)
+	}
+}
+
+// GetRootCommand returns the root cobra.Command for the application.
+func GetCommand() *cobra.Command {
+	return baseCmd
+}

internal/app/wwctl/overlay/root.go

@@ -10,6 +10,7 @@ import (
 	"github.com/hpcng/warewulf/internal/app/wwctl/overlay/imprt"
 	"github.com/hpcng/warewulf/internal/app/wwctl/overlay/list"
 	"github.com/hpcng/warewulf/internal/app/wwctl/overlay/mkdir"
+	"github.com/hpcng/warewulf/internal/app/wwctl/overlay/parse"
 	"github.com/hpcng/warewulf/internal/app/wwctl/overlay/show"
 	"github.com/spf13/cobra"
 )
@@ -17,9 +18,9 @@ import (
 var (
 	baseCmd = &cobra.Command{
 		DisableFlagsInUseLine: true,
-		Use:   "overlay COMMAND [OPTIONS]",
-		Short: "Warewulf Overlay Management",
-		Long:  "Management interface for Warewulf overlays",
+		Use:                   "overlay COMMAND [OPTIONS]",
+		Short:                 "Warewulf Overlay Management",
+		Long:                  "Management interface for Warewulf overlays",
 	}
 )
 
@@ -34,6 +35,8 @@ func init() {
 	baseCmd.AddCommand(imprt.GetCommand())
 	baseCmd.AddCommand(chmod.GetCommand())
 	baseCmd.AddCommand(chown.GetCommand())
+	baseCmd.AddCommand(parse.GetCommand())
+
 }
 
 // GetRootCommand returns the root cobra.Command for the application.