Following up on file-position locking

Even documentation right next to the code can go stale. At work I've seen it on more occasions than I can count that e.g. new flags or even new function parameters were not added to the documentation. The best effort I've seen to fix these kind of errors is the Elixir DocTest, where the examples in the documentation are actually executed by the unit test framework, so for example if a new function parameter is added (without a default value), the unit test(!) will catch if the documentation was not upgraded. It's far from 100% and there are code where unit testing is complicated, but it's still useful.