replace version subcommand with --version flag

Author: notnmeyer

cmd/build_info.go

@@ -0,0 +1,25 @@
+package cmd
+
+import (
+	"runtime/debug"
+	"strings"
+)
+
+var (
+	version = "dev"
+	commit  = "none"
+)
+
+func init() {
+	if info, ok := debug.ReadBuildInfo(); ok && version == "dev" {
+		if info.Main.Version != "" && info.Main.Version != "(devel)" {
+			version = strings.TrimPrefix(info.Main.Version, "v")
+		}
+		for _, s := range info.Settings {
+			if s.Key == "vcs.revision" && len(s.Value) >= 7 {
+				commit = s.Value[:7]
+				break
+			}
+		}
+	}
+}