synchroniser : add backup to sync_files

Adds the option to enable backup when synchronising.
This is done in sync_files by passing the appropriate arguments to sync.
For this we need to add an argument to sync_files as the backup
configuration options are needed.
The configuration options are imported from unisync.config.BackupConfig.
Also import typing.cast to be able to narrow down a type.

src/unisync/synchroniser.py

@@ -14,8 +14,10 @@ import time
 import logging
 
 from pathlib import Path
+from typing import cast
 
 from unisync.errors import RemoteMountedError, InvalidMountError
+from unisync.config import BackupConfig
 
 logger = logging.getLogger(__name__)
 
@@ -117,7 +119,9 @@ class Synchroniser:
         close = subprocess.Popen(command)
         return close.wait()
 
-    def sync_files(self, paths:list, force:bool=False) -> int:
+    def sync_files(self, paths:list, force:bool=False,
+                   backup:BackupConfig | None = None
+                   ) -> int:
         """Synchronises the files.
 
         Args:
@@ -127,11 +131,35 @@ class Synchroniser:
         Returns:
             The return code of sync.
         """
+        other = list()
+        if(backup != None and backup.enabled):
+            backup = cast(BackupConfig, backup)
+
+            other.append("-backup")
+            if(backup.selection != ""):
+                other.append(backup.selection)
+            else:
+                other.append("Name *")
+
+            other.append([
+                "-backuploc",
+                backup.location,
+                "-maxbackups",
+                backup.max_backups,
+                "-backupsuffix",
+                backup.backupsuffix,
+                "-backupprefix",
+                backup.backupprefix,
+                "-ignore",
+                backup.backupprefix
+            ])
+
         return self.sync(
                 f"ssh://{self.remote_user}@{self.remote_ip}/{self.remote_dir}/.data",
                 self.local,
                 paths=paths,
-                force=force
+                force=force,
+                other=other
                 )
 
     def sync_links(self, ignore:list) -> int: