Add a flag that prints version information

Resolves #51

ci/build.sh

@@ -1,9 +1,11 @@
 #!/bin/bash
 export GOARCH=amd64
 
+tag=$(git describe  --tags)
+
 build(){
 	tmpdir=$(mktemp -d)
-	go build -o $tmpdir/sshcode
+	go build -ldflags "-X main.version=${tag}" -o $tmpdir/sshcode
 
 	pushd $tmpdir
 	tarname=sshcode-$GOOS-$GOARCH.tar

main.go

@@ -55,11 +55,15 @@ func flagHelp() string {
 	return bd.String()
 }
 
+// version is overwritten by ci/build.sh.
+var version string
+
 func main() {
 	var (
 		skipSyncFlag = flag.Bool("skipsync", false, "skip syncing local settings and extensions to remote host")
 		sshFlags     = flag.String("ssh-flags", "", "custom SSH flags")
 		syncBack     = flag.Bool("b", false, "sync extensions back on termination")
+		printVersion = flag.Bool("version", false, "print version information and exit")
 	)
 
 	flag.Usage = func() {
@@ -81,6 +85,11 @@ Arguments:
 	}
 
 	flag.Parse()
+	if *printVersion {
+		fmt.Printf("%v\n", version)
+		os.Exit(0)
+	}
+
 	host := flag.Arg(0)
 
 	if host == "" {