cmd/ethkey: fix formatting, review nits (#15807)

This commit:

- Adds a --msgfile option to read the message to sign from a file
  instead of command line argument.
- Adds a unit test for signing subcommands.
- Removes some weird whitespace in the code.

cmd/ethkey/message_test.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 (
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+func TestMessageSignVerify(t *testing.T) {
+	tmpdir, err := ioutil.TempDir("", "ethkey-test")
+	if err != nil {
+		t.Fatal("Can't create temporary directory:", err)
+	}
+	defer os.RemoveAll(tmpdir)
+
+	keyfile := filepath.Join(tmpdir, "the-keyfile")
+	message := "test message"
+
+	// Create the key.
+	generate := runEthkey(t, "generate", keyfile)
+	generate.Expect(`
+!! Unsupported terminal, password will be echoed.
+Passphrase: {{.InputLine "foobar"}}
+Repeat passphrase: {{.InputLine "foobar"}}
+`)
+	_, matches := generate.ExpectRegexp(`Address: (0x[0-9a-fA-F]{40})\n`)
+	address := matches[1]
+	generate.ExpectExit()
+
+	// Sign a message.
+	sign := runEthkey(t, "signmessage", keyfile, message)
+	sign.Expect(`
+!! Unsupported terminal, password will be echoed.
+Passphrase: {{.InputLine "foobar"}}
+`)
+	_, matches = sign.ExpectRegexp(`Signature: ([0-9a-f]+)\n`)
+	signature := matches[1]
+	sign.ExpectExit()
+
+	// Verify the message.
+	verify := runEthkey(t, "verifymessage", address, signature, message)
+	_, matches = verify.ExpectRegexp(`
+Signature verification successful!
+Recovered public key: [0-9a-f]+
+Recovered address: (0x[0-9a-fA-F]{40})
+`)
+	recovered := matches[1]
+	verify.ExpectExit()
+
+	if recovered != address {
+		t.Error("recovered address doesn't match generated key")
+	}
+}