Add version command

main.go

@@ -52,6 +52,7 @@ type configParams struct {
 	NodeCacheFilename   string   `long:"node-cache-filename" description:"save and load other nodes information to this file, improves cold start performance"  json:"node_cache_filename" toml:"node_cache_filename"`
 	NodeCacheLifetime   int      `long:"node-cache-lifetime" description:"nodes with last update older than this time (in minutes) will be removed from cache after loading it" json:"node_cache_lifetime" toml:"node_cache_lifetime"`
 	NodeCacheInfo       bool     `long:"node-cache-info" description:"show red and cyan 'x' characters in routes to indicate node cache misses and hits respectively" json:"node_cache_info" toml:"node_cache_info"`
+	Version             bool     `short:"v" long:"version" description:"show program version and exit"`
 }
 
 var params, cfgParams configParams
@@ -329,7 +330,10 @@ func tryRapidRebalance(ctx context.Context, r *regolancer, from, to uint64, rout
 }
 
 func preflightChecks(params *configParams) error {
-
+	if params.Version {
+		printVersion()
+		os.Exit(1)
+	}
 	if params.Connect == "" {
 		params.Connect = "127.0.0.1:10009"
 	}

version.go

@@ -0,0 +1,28 @@
+package main
+
+import (
+	"fmt"
+	"os"
+	"runtime/debug"
+)
+
+func printVersion() {
+	info, ok := debug.ReadBuildInfo()
+	if !ok {
+		fmt.Printf("No build info available")
+	} else {
+		settings := map[string]string{}
+		for _, bs := range info.Settings {
+			settings[bs.Key] = bs.Value
+		}
+		version := info.Main.Version
+		if rev, ok := settings["vcs.revision"]; ok && version == "(devel)" {
+			version = "git" + rev[:8]
+		}
+		if settings["vcs.modified"] == "true" {
+			version += "-dirty"
+		}
+		fmt.Printf("Regolancer %s, built with %s\nSource: https://github.com/rkfg/regolancer\n", version, info.GoVersion)
+	}
+	os.Exit(1)
+}