Adds paths adding functionnality

Adds functions that allows adding new paths to the synchronisation.
When writing the new paths to the file if a parent directory is
synchronised all the childrens are removed.

src/unisync/paths.py

@@ -1,6 +1,8 @@
 # Copyright (C) 2025 Paul Retourné
 # SPDX-License-Identifier: GPL-3.0-or-later
 
+
+import os.path
 import subprocess
 
 from pathlib import Path, PosixPath
@@ -35,7 +37,10 @@ class PathsManager:
         Args:
             choice_timeout: Time given to make choices in nnn
         Returns:
-            list[str]: The list of paths that was selected
+            list[str]: The list of paths that was selected relative to the top directory
+        Raise:
+            TimeoutExpired: User took too long to choose
+            CalledProcessError: An unknown error occured during the selection
         """
         command = [
                 "/usr/bin/nnn",
@@ -62,6 +67,16 @@ class PathsManager:
             paths_list.append(next_path)
         return paths_list
 
+    def add_files_to_sync(self):
+        while true:
+            try:
+                paths = self.user_select_files()
+                break
+            except subprocess.TimeoutExpired:
+                if input("Timeout expired do you want to retry (y/n): ") != "y":
+                    raise
+        self.write_new_paths(paths)
+
     def get_paths_to_sync(self) -> list[str]:
         """
         Return the paths to synchronise as list.
@@ -71,4 +86,27 @@ class PathsManager:
             paths.pop()
         return paths
 
+    def write_new_paths(self, paths:list[str]):
+        """
+        Writes a list of new paths to the file
+        """
+        current_paths = self.get_paths_to_sync()
+        paths_to_add = list()
+        # Check if one of the parent is already being synchronised
+        # If so there is no need to add the child path
+        for new_path in paths:
+            is_contained = False
+            for existing in current_paths:
+                common = os.path.commonpath([new_path, existing])
+                if common == existing:
+                    is_contained = True
+                    break
+
+            if not is_contained and new_path not in paths_to_add:
+                paths_to_add.append(new_path)
+
+        with self.paths_file.open("w") as f:
+            for p in paths_to_add:
+                f.write(p + "\n")
+