fix ShowVersion (V/version) flag

add copyright notices

cmd/rebuilddb2/config.go

@@ -1,10 +1,15 @@
+// Copyright (c) 2018, The Decred developers
+// Copyright (c) 2017, The dcrdata developers
+// See LICENSE for details.
+
 package main
 
 import (
 	"fmt"
 	"os"
 	"path/filepath"
 	"regexp"
+	"runtime"
 	"strings"
 
 	flags "github.com/btcsuite/go-flags"
@@ -135,12 +140,13 @@ func loadConfig() (*config, error) {
 	}
 
 	// Show the version and exit if the version flag was specified.
-	// appName := filepath.Base(os.Args[0])
-	// appName = strings.TrimSuffix(appName, filepath.Ext(appName))
-	// if preCfg.ShowVersion {
-	// 	fmt.Println(appName, "version", ver.String())
-	// 	os.Exit(0)
-	// }
+	appName := filepath.Base(os.Args[0])
+	appName = strings.TrimSuffix(appName, filepath.Ext(appName))
+	if preCfg.ShowVersion {
+		fmt.Printf("%s version %s (Go version %s, %s-%s)\n", appName,
+			ver.String(), runtime.Version(), runtime.GOOS, runtime.GOARCH)
+		os.Exit(0)
+	}
 
 	// Load additional config from file.
 	var configFileError error

cmd/rebuilddb2/rebuilddb2.go

@@ -1,3 +1,7 @@
+// Copyright (c) 2018, The Decred developers
+// Copyright (c) 2017, The dcrdata developers
+// See LICENSE for details.
+
 package main
 
 import (

cmd/rebuilddb2/version.go

@@ -0,0 +1,38 @@
+// Copyright (c) 2018, The Decred developers
+// Copyright (c) 2017, The dcrdata developers
+// See LICENSE for details.
+
+package main
+
+import "fmt"
+
+type version struct {
+	Major, Minor, Patch int
+	Label               string
+	Nick                string
+}
+
+var ver = version{
+	Major: 2,
+	Minor: 0,
+	Patch: 0,
+	Label: ""}
+
+// CommitHash may be set on the build command line:
+// go build -ldflags "-X main.CommitHash=`git rev-parse --short HEAD`"
+var CommitHash string
+
+const appName string = "rebuilddb2"
+
+func (v *version) String() string {
+	var hashStr string
+	if CommitHash != "" {
+		hashStr = "+" + CommitHash
+	}
+	if v.Label != "" {
+		return fmt.Sprintf("%d.%d.%d-%s%s",
+			v.Major, v.Minor, v.Patch, v.Label, hashStr)
+	}
+	return fmt.Sprintf("%d.%d.%d%s",
+		v.Major, v.Minor, v.Patch, hashStr)
+}