Finding out which files a triggering a rebuild

[cmarqu]

Since the switch to https://watchfiles.helpmanual.io/, it is not easy to find out which files are triggering a rebuild.
There is WATCHFILES_DEBUG=1, but it's very verbose.

As a workaround, I have locally patched

sphinx-autobuild/sphinx_autobuild/filter.py

Line 25 in 86e2f37

normalised_path = Path(filename).resolve().as_posix()

with a print(f"File {normalised_path} has changed; ignores are {self}").

Such a line could be enabled by a new command line option or an environment variable like SPHINX_AUTOBUILD_DEBUG.

[AA-Turner]

Happy to accept a PR