Move download summary into a separate class

PFERD/download_summary.py

@@ -0,0 +1,50 @@
+class DownloadSummary:
+
+    def __init__(self):
+        self._new_files = []
+        self._changed_files = []
+        self._deleted_files = []
+
+    def merge(self, summary: 'DownloadSummary') -> None:
+        self._new_files += summary._new_files
+        self._changed_files += summary._changed_files
+        self._deleted_files += summary._deleted_files
+
+    def add_deleted_file(self, path) -> None:
+        self._deleted_files.append(path)
+
+    def add_changed_file(self, path) -> None:
+        self._changed_files.append(path)
+
+    def add_new_file(self, path) -> None:
+        self._new_files.append(path)
+
+    def _has_no_updates(self) -> bool:
+        return len(self._new_files) == 0 and len(self._changed_files) == 0 and len(self._deleted_files) == 0
+
+    def print(self, logger, pretty) -> None:
+        logger.info("")
+        logger.info("Summary: ")
+        if self._has_no_updates():
+            logger.info("nothing changed")
+        else:
+            if len(self._new_files) > 0:
+                logger.info("New Files:")
+                for file in self._new_files:
+                    pretty.new_file(file)
+
+            logger.info("")
+
+            if len(self._changed_files) > 0:
+                logger.info("Modified Files:")
+                for file in self._changed_files:
+                    pretty.modified_file(file)
+
+            logger.info("")
+
+            if len(self._deleted_files) > 0:
+                logger.info("Deleted Files:")
+                for file in self._deleted_files:
+                    pretty.deleted_file(file)
+
+        logger.info("")