Add version information and -V/--version flags.

config.go

@@ -12,6 +12,7 @@ import (
 	"net"
 	"os"
 	"path/filepath"
+	"strings"
 	"time"
 )
 
@@ -33,6 +34,7 @@ var (
 //
 // See loadConfig for details on the configuration load process.
 type config struct {
+	ShowVersion    bool          `short:"V" long:"version" description:"Display version information and exit"`
 	ConfigFile     string        `short:"C" long:"configfile" description:"Path to configuration file"`
 	DbDir          string        `short:"b" long:"dbdir" description:"Directory to store database"`
 	AddPeers       []string      `short:"a" long:"addpeer" description:"Add a peer to connect with at startup"`
@@ -177,7 +179,7 @@ func loadConfig() (*config, []string, error) {
 	}
 
 	// Pre-parse the command line options to see if an alternative config
-	// file was specified.
+	// file or the version flag was specified.
 	preCfg := cfg
 	preParser := flags.NewParser(&preCfg, flags.Default)
 	_, err := preParser.Parse()
@@ -188,6 +190,14 @@ func loadConfig() (*config, []string, error) {
 		return nil, nil, err
 	}
 
+	// Show the version and exit if the version flag was specified.
+	if preCfg.ShowVersion {
+		appName := filepath.Base(os.Args[0])
+		appName = strings.TrimSuffix(appName, filepath.Ext(appName))
+		fmt.Println(appName, "version", version())
+		os.Exit(0)
+	}
+
 	// Load additional config from file.
 	parser := flags.NewParser(&cfg, flags.Default)
 	err = parser.ParseIniFile(preCfg.ConfigFile)

version.go

@@ -0,0 +1,72 @@
+// Copyright (c) 2013 Conformal Systems LLC.
+// Use of this source code is governed by an ISC
+// license that can be found in the LICENSE file.
+
+package main
+
+import (
+	"bytes"
+	"fmt"
+	"strings"
+)
+
+// semanticAlphabet
+const semanticAlphabet = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz-"
+
+// These constants define the application version and follow the semantic
+// versioning 2.0.0 spec (http://semver.org/).
+const (
+	appMajor uint = 0
+	appMinor uint = 1
+	appPatch uint = 0
+
+	// appPreRelease MUST only contain characters from semanticAlphabet
+	// per the semantic versioning spec.
+	appPreRelease = "alpha"
+)
+
+// appBuild is defined as a variable so it can be overridden during the build
+// process with '-ldflags "-X main.appBuild foo' if needed.  It MUST only
+// contain characters from semanticAlphabet per the semantic versioning spec.
+var appBuild string
+
+// version returns the application version as a properly formed string per the
+// semantic versioning 2.0.0 spec (http://semver.org/).
+func version() string {
+	// Start with the major, minor, and path versions.
+	version := fmt.Sprintf("%d.%d.%d", appMajor, appMinor, appPatch)
+
+	// Append pre-release version if there is one.  The hyphen called for
+	// by the semantic versioning spec is automatically appended and should
+	// not be contained in the pre-release string.  The pre-release version
+	// is not appended if it contains invalid characters.
+	preRelease := normalizeVerString(appPreRelease)
+	if preRelease != "" {
+		version = fmt.Sprintf("%s-%s", version, preRelease)
+	}
+
+	// Append build metadata if there is any.  The plus called for
+	// by the semantic versioning spec is automatically appended and should
+	// not be contained in the build metadata string.  The build metadata
+	// string is not appended if it contains invalid characters.
+	build := normalizeVerString(appBuild)
+	if build != "" {
+		version = fmt.Sprintf("%s+%s", version, build)
+	}
+
+	return version
+}
+
+// normalizeVerString returns the passed string stripped of all characters which
+// are not valid according to the semantic versioning guidelines for pre-release
+// version and build metadata strings.  In particular they MUST only contain
+// characters in semanticAlphabet.
+func normalizeVerString(str string) string {
+	var result bytes.Buffer
+	for _, r := range str {
+		if strings.ContainsRune(semanticAlphabet, r) {
+			result.WriteRune(r)
+		}
+	}
+	return result.String()
+}