Show our version with "-v".

This will be set to our release-tag, and commit-revision, when
the release pipeline runs.

This closes #51.

.github/build

@@ -42,7 +42,7 @@ for OS in ${BUILD_PLATFORMS[@]}; do
         export CGO_ENABLED=0
 
         # Build the main-binary
-        go build -ldflags "-X main.version=$(git describe --tags 2>/dev/null || echo 'master')" -o "${BASE}-${SUFFIX}"
+        go build -ldflags "-X main.version=$(git describe --tags 2>/dev/null || echo 'master') -X main.sha1sum=$(git rev-parse HEAD)" -o "${BASE}-${SUFFIX}"
 
     done
 done

main.go

@@ -24,6 +24,11 @@ import (
 	"github.com/skx/yal/stdlib"
 )
 
+var (
+	version = "unreleased"
+	sha1sum = "unknown"
+)
+
 func main() {
 
 	// (gensym) needs a decent random seed, as does (random).
@@ -32,8 +37,15 @@ func main() {
 	// Look to see if we're gonna execute a statement, or dump our help.
 	exp := flag.String("e", "", "A string to evaluate.")
 	hlp := flag.Bool("h", false, "Should we show help information, and exit?")
+	ver := flag.Bool("v", false, "Should we show our version, and exit?")
 	flag.Parse()
 
+	// Showing the version?
+	if *ver {
+		fmt.Printf("%s [%s]\n", version, sha1sum)
+		return
+	}
+
 	// Ensure we have an argument, if we don't have flags.
 	if len(flag.Args()) < 1 && (*exp == "") && !*hlp {
 		fmt.Printf("Usage: yal [-e expr] [-h] file.lisp\n")