added native copy command for multi-arch support

command/copy.go

@@ -0,0 +1,74 @@
+// Copyright 2019 Drone.IO Inc. All rights reserved.
+// Use of this source code is governed by the Polyform License
+// that can be found in the LICENSE file.
+
+package command
+
+import (
+	"io"
+	"os"
+
+	"gopkg.in/alecthomas/kingpin.v2"
+)
+
+type copyCommand struct {
+	source string
+	target string
+}
+
+func (c *copyCommand) run(*kingpin.ParseContext) error {
+	return Copy(c.source, c.target)
+}
+
+func Copy(src, dst string) error {
+	in, err := os.Open(src)
+	if err != nil {
+		return err
+	}
+	defer in.Close()
+
+	out, err := os.Create(dst)
+	if err != nil {
+		return err
+	}
+	defer out.Close()
+
+	_, err = io.Copy(out, in)
+	if err != nil {
+		return err
+	}
+
+	err = out.Sync()
+	if err != nil {
+		return err
+	}
+
+	info, err := os.Stat(src)
+	if err != nil {
+		return err
+	}
+
+	err = os.Chmod(dst, info.Mode())
+	if err != nil {
+		return err
+	}
+
+	return out.Close()
+}
+
+// Register registers the copy command.
+func registerCopy(app *kingpin.Application) {
+	c := new(copyCommand)
+
+	cmd := app.Command("copy", "entrypoint copy").
+		Hidden().
+		Action(c.run)
+
+	cmd.Flag("source", "source binary path").
+		Default("/bin/tmate").
+		StringVar(&c.source)
+
+	cmd.Flag("target", "target binary path").
+		Default("/usr/drone/bin/tmate").
+		StringVar(&c.target)
+}