anchor.diff:    (write-all-mode! path true false data))
   
   (defun append-lines! (path data)
  -  "Appends the lines (list of strings) `data` to the file at `path`.
  +  "Appends the lines (list of strings) `data` to the file at `PATH`.
      Creates a new file if it doesn't exist.
      Returns true if it succeeded or false if it failed.
   
  
positive.code:     data))
  
  (defun read-all! (path) 
    "Reads the data from the file at `path` and returns it as a string.
     Returns nil if it failed.
  
     ### Example
  
negative.code:   (read-all-mode! path false))
  
  (defun read-lines! (path) 
    "Reads the lines from the file at `PATH` and returns it as a list of strings.
     Returns nil if it failed.
  
     ### Example
  