Add version flag

main.go

@@ -3,10 +3,12 @@ package main
 import (
 	"bufio"
 	"flag"
+	"fmt"
 	"io"
 	"log"
 	"os"
 	"path/filepath"
+	"runtime/debug"
 	"sync/atomic"
 
 	utils "git.site.quack-lab.dev/dave/cyutils"
@@ -20,18 +22,27 @@ const ImportantColor = BRed
 const DefaultColor = Reset
 const PathColor = Green
 
-var programName = os.Args[0]
-var undo = false
+var (
+	programName = os.Args[0]
+	undo        = false
+	version     = "dev"
+)
 
 func main() {
 	recurse := flag.String("r", "", "recurse into directories")
 	file := flag.String("f", "", "file to read instructions from")
 	debug := flag.Bool("d", false, "debug")
 	undoF := flag.Bool("u", false, "undo")
+	versionFlag := flag.Bool("v", false, "print version and exit")
 	dryRun := flag.Bool("n", false, "dry run (no filesystem changes)")
 	flag.Parse()
 	undo = *undoF
 
+	if *versionFlag {
+		fmt.Println(getVersionString())
+		return
+	}
+
 	setupLogging(*debug)
 
 	if *dryRun {
@@ -248,6 +259,44 @@ func ReadFromFilesRecursively(input string, output chan *LinkInstruction, status
 	}
 }
 
+func getVersionString() string {
+	if version != "" && version != "dev" {
+		return version
+	}
+
+	if info, ok := debug.ReadBuildInfo(); ok {
+		if info.Main.Version != "" && info.Main.Version != "(devel)" {
+			return info.Main.Version
+		}
+
+		var revision, modified, vcsTime string
+		for _, setting := range info.Settings {
+			switch setting.Key {
+			case "vcs.revision":
+				revision = setting.Value
+			case "vcs.modified":
+				modified = setting.Value
+			case "vcs.time":
+				vcsTime = setting.Value
+			}
+		}
+		if revision != "" {
+			if len(revision) > 7 {
+				revision = revision[:7]
+			}
+			if modified == "true" {
+				revision += "-dirty"
+			}
+			if vcsTime != "" {
+				revision += " (" + vcsTime + ")"
+			}
+			return revision
+		}
+	}
+
+	return "dev"
+}
+
 func ReadFromFile(input string, output chan *LinkInstruction, status chan error, doclose bool) {
 	if doclose {
 		defer close(output)