cmd/ethkey: new command line tool for keys (#15438)

ethkey is a new tool that serves as a command line interface to
the basic key management functionalities of geth. It currently
supports:
 
 - generating keyfiles
 - inspecting keyfiles (print public and private key)
 - signing messages
 - verifying signed messages

cmd/ethkey/main.go

@@ -0,0 +1,70 @@
+// Copyright 2017 The go-ethereum Authors
+// This file is part of go-ethereum.
+//
+// go-ethereum is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// go-ethereum is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with go-ethereum. If not, see <http://www.gnu.org/licenses/>.
+
+package main
+
+import (
+	"fmt"
+	"os"
+
+	"github.com/ethereum/go-ethereum/cmd/utils"
+	"gopkg.in/urfave/cli.v1"
+)
+
+const (
+	defaultKeyfileName = "keyfile.json"
+)
+
+var (
+	gitCommit = "" // Git SHA1 commit hash of the release (set via linker flags)
+
+	app *cli.App // the main app instance
+)
+
+var ( // Commonly used command line flags.
+	passphraseFlag = cli.StringFlag{
+		Name:  "passwordfile",
+		Usage: "the file that contains the passphrase for the keyfile",
+	}
+
+	jsonFlag = cli.BoolFlag{
+		Name:  "json",
+		Usage: "output JSON instead of human-readable format",
+	}
+
+	messageFlag = cli.StringFlag{
+		Name:  "message",
+		Usage: "the file that contains the message to sign/verify",
+	}
+)
+
+// Configure the app instance.
+func init() {
+	app = utils.NewApp(gitCommit, "an Ethereum key manager")
+	app.Commands = []cli.Command{
+		commandGenerate,
+		commandInspect,
+		commandSignMessage,
+		commandVerifyMessage,
+	}
+}
+
+func main() {
+	if err := app.Run(os.Args); err != nil {
+		fmt.Fprintln(os.Stderr, err)
+		os.Exit(1)
+	}
+}