Module backup 

Backup creation under $DOTFILES/.yui/backup/.

Path scheme: mirror the absolute target path (drive colon stripped on Windows), then suffix the basename with a timestamp before the extension.

  target  C:\Users\u\.config\foo\bar.yml
  backup  $DOTFILES/.yui/backup/C/Users/u/.config/foo/bar_20260429_143022123.yml

Functions

backup_dir

Recursively copy src (a directory tree) to dest. Symlinks within the tree are skipped (we’d be copying their targets again redundantly, and link semantics don’t carry meaning in a backup).

backup_file

Copy src (a regular file) to dest, creating parent dirs as needed.

backup_path

current_timestamp

Format the current local time using a jiff strtime pattern.