internal/restorer: invert dependency direction to ui/restorer

The restorer imported ui/restorer which leaks ui logic into the restorer
core. Swap the direction by letting the restorer use a ProgressReporter
interface + associated constants.

internal/restorer/progress.go

@@ -0,0 +1,38 @@
+package restorer
+
+type ItemAction string
+
+// Constants for the different CompleteItem actions.
+const (
+	ActionDirRestored   ItemAction = "dir restored"
+	ActionFileRestored  ItemAction = "file restored"
+	ActionFileUpdated   ItemAction = "file updated"
+	ActionFileUnchanged ItemAction = "file unchanged"
+	ActionOtherRestored ItemAction = "other restored"
+	ActionDeleted       ItemAction = "deleted"
+)
+
+// ProgressReporter reports restore progress.
+type ProgressReporter interface {
+	AddFile(size uint64)
+	AddProgress(name string, action ItemAction, bytesWrittenPortion, bytesTotal uint64)
+	AddSkippedFile(name string, size uint64)
+	ReportDeletion(name string)
+}
+
+type noopProgressReporter struct{}
+
+var _ ProgressReporter = (*noopProgressReporter)(nil)
+
+func (noopProgressReporter) AddFile(uint64) {}
+func (noopProgressReporter) AddProgress(string, ItemAction, uint64, uint64) {
+}
+func (noopProgressReporter) AddSkippedFile(string, uint64) {}
+func (noopProgressReporter) ReportDeletion(string)         {}
+
+func progressOrNoop(p ProgressReporter) ProgressReporter {
+	if p == nil {
+		return noopProgressReporter{}
+	}
+	return p
+}