Replacing a file while preserving the previous version

We can leverage the power of pathlib to support a variety of filename manipulations. In the Using pathlib to work with filenames recipe, we looked at a few of the most common techniques of managing directories, filenames, and file suffixes.

One common file processing requirement is to create output files in a fail-safe manner. That is, the application should preserve any previous output file no matter how or where the application fails.

Consider the following scenario:

1. At time t₀ there's a valid output.csv file from yesterday's use of the long_complex.py application.
2. At time t₁ we start running the long_complex.py application. It begins overwriting the output.csv file. It is expected to finish normally at time t₃.
3. At time t₂, the application crashes. The partial output.csv file is useless. Worse, the valid file from time t₀ is not available either, since it was overwritten.

Clearly, we can make backup copies of files. This introduces an extra...