append(true)

Append to File rather than truncating the data if the file exists.

The File is opened using lock(exclusive), which implies that, provided the OS and file system implements file locking, multiple processes may save coverage data to the same file.

The saved data is highly specific to the setup in which it has been created. It can typically only be reloaded using cov_load_data/2 in the same Prolog executable using the same options and with all relevant source file unmodified at the same location.

Reproducibility can be improved by using `.qlf` files or saved states.