cmd/age-keygen: move to a standalone binary

cmd/age-keygen/keygen.go

@@ -0,0 +1,51 @@
+// Copyright 2019 Google LLC
+//
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file or at
+// https://developers.google.com/open-source/licenses/bsd
+
+package main
+
+import (
+	"flag"
+	"fmt"
+	"io"
+	"log"
+	"os"
+	"time"
+
+	"github.com/FiloSottile/age/internal/age"
+)
+
+func main() {
+	log.SetFlags(0)
+
+	outFlag := flag.String("o", "", "output to `FILE` (default stdout)")
+	flag.Parse()
+	if len(flag.Args()) != 0 {
+		log.Fatalf("age-keygen takes no arguments")
+	}
+
+	out := os.Stdout
+	if name := *outFlag; name != "" {
+		f, err := os.OpenFile(name, os.O_WRONLY|os.O_CREATE|os.O_EXCL, 0600)
+		if err != nil {
+			log.Fatalf("Failed to open output file %q: %v", name, err)
+		}
+		defer f.Close()
+		out = f
+	}
+
+	generate(out)
+}
+
+func generate(out io.Writer) {
+	k, err := age.GenerateX25519Identity()
+	if err != nil {
+		log.Fatalf("Internal error: %v", err)
+	}
+
+	fmt.Fprintf(out, "# created: %s\n", time.Now().Format(time.RFC3339))
+	fmt.Fprintf(out, "# %s\n", k.Recipient())
+	fmt.Fprintf(out, "%s\n", k)
+}