My PR https://github.com/python/cpython/pull/3106 failed because patchcheck wants me to normalize spaces of Modules/expat/siphash.h, whereas this file is copied from libexpat: see bpo-30947.

Attached PR changes Tools/scripts/patchcheck.py to ignore changes in Modules/expat/ and Modules/zlib/ subdirectories. The change also drops support for Mercurial, since CPython migrated to Git.

Is it worth to add other imported libs (libmpdec, libffi)? Or may be just remove trailing spaces when import sources from upstream?

Serhiy: "Is it worth to add other imported libs (libmpdec, libffi)?"

Oh right, I forgot libmpdec: I updated my PR.

By the way, I started a list of embedded libraries:
http://haypo-notes.readthedocs.io/cpython.html#embedded-libraries

* zlib
* expat
* libmpdec
* libffi

libffi should be excluded in Python 2.7 and 3.6, but it was removed from Python 3.7.


Serhiy: "Or may be just remove trailing spaces when import sources from upstream?"

I prefer to leave the copied code unchanged, so it allows to easily cherry-pick from upstream. I did that once for libexpat (for fix a compilation issue on Visual Studio 2008).

> libffi should be excluded in Python 2.7 and 3.6, but it was removed from Python 3.7.

The parts for OSX and MSVC still are in the source tree.

As for dropping support for Mercurial, is patchcheck.py used in other Python implementations (PyPy, Jython) which still use Mercurial?

Yes, please add libmpdec to the ignored files.

Serhiy: "The parts for OSX and MSVC still are in the source tree."

Oh, I didn't know that we still had two special libffi directories for macOS and Windows!

Why do we still have these directories? Both seems to be very outdated, no?

I completed my list:
http://haypo-notes.readthedocs.io/cpython.html#embedded-libraries


Serhiy: "As for dropping support for Mercurial, is patchcheck.py used in other Python implementations (PyPy, Jython) which still use Mercurial?"

I reverted my change to keep Mercurial support.

Stefan Krah: "Yes, please add libmpdec to the ignored files."

Ok, (already) done.

New changeset 4a347ce426fe7381885703d9074d7a6b3aeb2f2b by Victor Stinner in branch 'master':
bpo-31221: patchcheck ignores external libraries (#3109)
https://github.com/python/cpython/commit/4a347ce426fe7381885703d9074d7a6b3aeb2f2b

New changeset d23b1c4fd82a326e729027a791220d6011e097b4 by Victor Stinner in branch '3.6':
[3.6] bpo-31221: patchcheck ignores external libraries (#3109) (#3116)
https://github.com/python/cpython/commit/d23b1c4fd82a326e729027a791220d6011e097b4

New changeset d45cb040b9fcd74e8824d417bf789fcef4c9592c by Victor Stinner in branch '2.7':
[2.7] bpo-31221: patchcheck ignores external libraries (#3109) (#3118)
https://github.com/python/cpython/commit/d45cb040b9fcd74e8824d417bf789fcef4c9592c

patchcheck fixed in 2.7, 3.6 and 3.7 master.