Only add files with modification outside doc blocks
# What does this PR do?

Add files for doctesting only when they have modifications outside docstrings.

(offline message from Sylvain)
> One small improvement I see is for the docstrings: for now the tests are launched on a file if we modify it, but I would only launch it if docstrings are modified (e.g. check the modifications are correct) to go faster. If changes in the code of a model file (for instance) trigger a doctest failure we will see it after. 
_The documentation is not available anymore as the PR was closed or merged._