move config migration to its own file

tljh/migrator.py

@@ -0,0 +1,69 @@
+"""Migration utilities for upgrading tljh"""
+
+import os
+from datetime import date
+import logging
+import shutil
+
+from tljh.config import (
+    CONFIG_DIR,
+    CONFIG_FILE,
+    INSTALL_PREFIX,
+)
+
+
+logger = logging.getLogger(__name__)
+
+
+def migrate_file(old_path, new_path):
+    """Migrate one file from an old location to a new one
+
+    avoids collisions if the new file exists
+    """
+    if not os.path.exists(old_path):
+        return
+    if os.path.exists(new_path):
+        # new config file already created! still move the config,
+        # but avoid collision
+        timestamp = date.today().isoformat()
+        dest = dest_base = f"{new_path}.old.{timestamp}"
+        i = 0
+        while os.path.exists(dest):
+            # avoid collisions
+            dest = dest_base + f".{i}"
+            i += 1
+        logger.warning(f"Found file in both old ({old_path}) and new ({new_path}).")
+        logger.warning(
+            f"Moving {old_path} to {dest} to avoid clobbering.  Its contents will be ignored."
+        )
+    else:
+        dest = new_path
+    shutil.move(old_path, dest)
+
+
+def migrate_directory(old_dir, new_dir):
+    """Migrate a directory to a new location"""
+    if not os.path.exists(old_dir):
+        return
+    if os.path.exists(new_dir):
+        # both dirs exist
+        for f in os.listdir(old_dir):
+            src = os.path.join(old_dir, f)
+            dest = os.path.join(new_dir, f)
+            if os.path.isdir(src):
+                migrate_directory(src, dest)
+            else:
+                migrate_file(src, dest)
+    else:
+        logger.warning(f"Moving directory to new location {old_dir} -> {new_dir}")
+        shutil.move(old_dir, new_dir)
+
+
+def migrate_config_files():
+    """Migrate config files to their new locations"""
+    # handle old TLJH_DIR/config.yaml location
+    migrate_file(os.path.join(INSTALL_PREFIX, "config.yaml"), CONFIG_FILE)
+    migrate_directory(
+        os.path.join(INSTALL_PREFIX, "jupyterhub_config.d"),
+        os.path.join(CONFIG_DIR, "jupyterhub_config.d"),
+    )