vmconfiger: minor cleanups

Use helper function instead of generating the same code every time. Move
header from a bunch of printfs to single template.

src/vmconfiger/generator.go

@@ -76,7 +76,8 @@ func (g *Generator) Format() []byte {
 func (g *Generator) Run() error {
 	fs := token.NewFileSet()
 
-	t := template.Must(template.New("funcs").Parse(funcsTemplate))
+	t := template.Must(template.New("header").Parse(headerTemplate))
+	template.Must(t.New("funcs").Parse(funcsTemplate))
 	template.Must(t.New("clear").Parse(clearTemplate))
 	// template name must match the type it intends to generate
 	template.Must(t.New("int64").Parse(numTemplate))
@@ -107,19 +108,12 @@ func (g *Generator) Run() error {
 	}
 
 	// Print the header and package clause.
-	g.Printf("// Code generated by \"vmconfiger %s\"; DO NOT EDIT\n\n", strings.Join(os.Args[1:], " "))
-	g.Printf("package %s\n", g.pkg.Name)
-	g.Printf(`import (
-	"fmt"
-	"minicli"
-	log "minilog"
-	"bytes"
-	"os"
-	"path/filepath"
-	"strconv"
-)`)
-	g.Printf("\n")
-	g.Printf("var vmconfigerCLIHandlers = []minicli.Handler{\n")
+	g.Execute("header", struct {
+		Args, Package string
+	}{
+		Args:    strings.Join(os.Args[1:], " "),
+		Package: g.pkg.Name,
+	})
 
 	g.fields = map[string][]Field{}