Add the .git dir back into the revad image

- So we can pass the version & git sha on the build process.
- Also return 0 on 'revad -version'

.dockerignore

@@ -1,5 +1,4 @@
 .github
-.git
 changelog
 docs
 examples

cmd/revad/main.go

@@ -86,7 +86,7 @@ func main() {
 func handleVersionFlag() {
 	if *versionFlag {
 		fmt.Fprintf(os.Stderr, "%s\n", getVersionString())
-		os.Exit(1)
+		os.Exit(0)
 	}
 }