Add option to preserve digests on copy

When enabled, if digests can't be preserved an error will be raised.

Signed-off-by: James Hewitt <james.hewitt@uk.ibm.com>

vendor/github.com/opencontainers/selinux/go-selinux/selinux.go

@@ -61,16 +61,30 @@ func ClassIndex(class string) (int, error) {
 	return classIndex(class)
 }
 
-// SetFileLabel sets the SELinux label for this path or returns an error.
+// SetFileLabel sets the SELinux label for this path, following symlinks,
+// or returns an error.
 func SetFileLabel(fpath string, label string) error {
 	return setFileLabel(fpath, label)
 }
 
-// FileLabel returns the SELinux label for this path or returns an error.
+// LsetFileLabel sets the SELinux label for this path, not following symlinks,
+// or returns an error.
+func LsetFileLabel(fpath string, label string) error {
+	return lSetFileLabel(fpath, label)
+}
+
+// FileLabel returns the SELinux label for this path, following symlinks,
+// or returns an error.
 func FileLabel(fpath string) (string, error) {
 	return fileLabel(fpath)
 }
 
+// LfileLabel returns the SELinux label for this path, not following symlinks,
+// or returns an error.
+func LfileLabel(fpath string) (string, error) {
+	return lFileLabel(fpath)
+}
+
 // SetFSCreateLabel tells the kernel what label to use for all file system objects
 // created by this task.
 // Set the label to an empty string to return to the default label. Calls to SetFSCreateLabel