Add tool for generating licenses for 3rd party deps

hack/licenser/README.md

@@ -0,0 +1,14 @@
+# Licenser
+
+This tool is used to generate file `NOTICE.txt` which contains certain notices of software components included in ECK.
+
+## Usage
+
+Tool is designed to work with [Go modules](https://github.com/golang/go/wiki/Modules) for managing dependencies, i.e. it requires Go 1.11+ to work. It expects to have all dependencies downloaded in `vendor` directory and file `vendor/modules.txt` exists. It can be achieved by running `go mod vendor`     
+
+To run it use:
+```go
+go mod vendor 
+cd hack/licenser
+go run main.go -d path/to/repo
+```

hack/licenser/main.go

@@ -0,0 +1,131 @@
+// Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+// or more contributor license agreements. Licensed under the Elastic License;
+// you may not use this file except in compliance with the Elastic License.
+
+package main
+
+import (
+	"bufio"
+	"flag"
+	"fmt"
+	"io/ioutil"
+	"log"
+	"os"
+	"path/filepath"
+	"strings"
+	"text/template"
+)
+
+var (
+	depFile = flag.String("f", "modules.txt", "File with the list of dependencies")
+	dir     = flag.String("d", "", "Project directory")
+)
+
+type Dependency struct {
+	Name    string
+	Version string
+	License string
+}
+
+type Dependencies struct {
+	List []*Dependency
+}
+
+func main() {
+	flag.Parse()
+	log.SetFlags(log.LstdFlags | log.Lshortfile)
+
+	deps, err := loadFile(filepath.Join(*dir, "vendor", *depFile))
+	if err != nil {
+		log.Fatalf("Can't open file with dependencies: %s", err.Error())
+	}
+
+	issues := checkForLicense(deps)
+	if issues > 0 {
+		log.Fatal("Can't create NOTICE.txt, there are issues with dependencies!")
+	}
+
+	createNoticeFile(deps)
+}
+
+func loadFile(path string) (*Dependencies, error) {
+	f, err := os.Open(path)
+	if err != nil {
+		return nil, err
+	}
+	defer f.Close()
+
+	deps := &Dependencies{}
+	scanner := bufio.NewScanner(f)
+	for scanner.Scan() {
+		line := scanner.Text()
+		if strings.HasPrefix(line, "#") {
+			dep := strings.Split(line, " ")
+			deps.List = append(deps.List, &Dependency{Name: dep[1], Version: dep[2]})
+		}
+	}
+
+	return deps, nil
+}
+
+func checkForLicense(deps *Dependencies) int {
+	var issues []string
+	licenses := []string{"LICENSE", "LICENSE.txt", "LICENCE"} // Used to keep all possible names of license files
+	for _, dep := range deps.List {
+		counter := len(licenses)
+		for _, v := range licenses {
+			bytes, err := ioutil.ReadFile(filepath.Join(*dir, "vendor", dep.Name, v))
+			if err != nil {
+				counter--
+				continue
+			}
+			dep.License = string(bytes)
+			break
+		}
+		if counter == 0 {
+			issues = append(issues, fmt.Sprintf("Can't find file with license for %s version %s", dep.Name, dep.Version))
+		}
+	}
+
+	if len(issues) > 0 {
+		fmt.Println("Number of issues:", len(issues))
+		for _, v := range issues {
+			fmt.Println(v)
+		}
+	}
+
+	return len(issues)
+}
+
+func createNoticeFile(deps *Dependencies) {
+	var tmpl = `Elastic Cloud on Kubernetes
+Copyright 2014-2019 Elasticsearch BV
+
+This product includes software developed by The Apache Software 
+Foundation (http://www.apache.org/).
+
+==========================================================================
+Third party libraries used by the Elastic Cloud on Kubernetes project:
+==========================================================================
+
+{{range $i,$v := .}} 
+Dependency: {{ $v.Name }}
+Version: {{ $v.Version }}
+
+{{ $v.License }}
+--------------------------------------------------------------------------
+{{end}}
+`
+	f, err := os.Create(filepath.Join(*dir, "NOTICE.txt"))
+	if err != nil {
+		log.Fatalf("Can't create NOTICE.txt: %s", err.Error())
+	}
+
+	t := template.Must(template.New("notice").Parse(tmpl))
+	err = t.Execute(f, deps.List)
+	if err != nil {
+		log.Fatalf("Failed on creating list of licenses for dependencies: %s", err.Error())
+	}
+
+	fmt.Println("NOTICE.txt was generated!")
+}