Add DeepCopyFile for copies with additional permission bits

It's not needed for most of all the copying we do, except when we
generate the deltas

See also #204

pkg/compiler/types/artifact/artifact.go

@@ -27,7 +27,6 @@ import (
 	"path/filepath"
 	"regexp"
 
-	system "github.com/docker/docker/pkg/system"
 	zstd "github.com/klauspost/compress/zstd"
 	gzip "github.com/klauspost/pgzip"
 
@@ -584,47 +583,16 @@ type CopyJob struct {
 	Artifact string
 }
 
-func copyXattr(srcPath, dstPath, attr string) error {
-	data, err := system.Lgetxattr(srcPath, attr)
-	if err != nil {
-		return err
-	}
-	if data != nil {
-		if err := system.Lsetxattr(dstPath, attr, data, 0); err != nil {
-			return err
-		}
-	}
-	return nil
-}
-
-func doCopyXattrs(srcPath, dstPath string) error {
-	if err := copyXattr(srcPath, dstPath, "security.capability"); err != nil {
-		return err
-	}
-
-	return copyXattr(srcPath, dstPath, "trusted.overlay.opaque")
-}
-
 func worker(i int, wg *sync.WaitGroup, s <-chan CopyJob) {
 	defer wg.Done()
 
 	for job := range s {
-		//Info("#"+strconv.Itoa(i), "copying", job.Src, "to", job.Dst)
-		// if dir, err := helpers.IsDirectory(job.Src); err == nil && dir {
-		// 	err = helpers.CopyDir(job.Src, job.Dst)
-		// 	if err != nil {
-		// 		Warning("Error copying dir", job, err)
-		// 	}
-		// 	continue
-		// }
-
 		_, err := os.Lstat(job.Dst)
 		if err != nil {
 			Debug("Copying ", job.Src)
-			if err := helpers.CopyFile(job.Src, job.Dst); err != nil {
+			if err := helpers.DeepCopyFile(job.Src, job.Dst); err != nil {
 				Warning("Error copying", job, err)
 			}
-			doCopyXattrs(job.Src, job.Dst)
 		}
 	}
 }

pkg/helpers/file.go

@@ -27,6 +27,7 @@ import (
 	"syscall"
 	"time"
 
+	"github.com/docker/docker/pkg/system"
 	"github.com/google/renameio"
 	copy "github.com/otiai10/copy"
 	"github.com/pkg/errors"
@@ -196,12 +197,39 @@ func EnsureDir(fileName string) error {
 	return nil
 }
 
-// CopyFile copies the contents of the file named src to the file named
+func CopyFile(src, dst string) (err error) {
+	return copy.Copy(src, dst, copy.Options{
+		Sync:      true,
+		OnSymlink: func(string) copy.SymlinkAction { return copy.Shallow }})
+}
+
+func copyXattr(srcPath, dstPath, attr string) error {
+	data, err := system.Lgetxattr(srcPath, attr)
+	if err != nil {
+		return err
+	}
+	if data != nil {
+		if err := system.Lsetxattr(dstPath, attr, data, 0); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func doCopyXattrs(srcPath, dstPath string) error {
+	if err := copyXattr(srcPath, dstPath, "security.capability"); err != nil {
+		return err
+	}
+
+	return copyXattr(srcPath, dstPath, "trusted.overlay.opaque")
+}
+
+// DeepCopyFile copies the contents of the file named src to the file named
 // by dst. The file will be created if it does not already exist. If the
 // destination file exists, all it's contents will be replaced by the contents
 // of the source file. The file mode will be copied from the source and
 // the copied data is synced/flushed to stable storage.
-func CopyFile(src, dst string) (err error) {
+func DeepCopyFile(src, dst string) (err error) {
 	// Workaround for https://github.com/otiai10/copy/issues/47
 	fi, err := os.Lstat(src)
 	if err != nil {
@@ -237,7 +265,8 @@ func CopyFile(src, dst string) (err error) {
 			fmt.Println("warning: failed chowning", dst, err.Error())
 		}
 	}
-	return err
+
+	return doCopyXattrs(src, dst)
 }
 
 func IsDirectory(path string) (bool, error) {