While iterating the context (once), multiple sources can be dispatched.
So if we get a timeout and shortly after the weak-ref callback, then
we still need to honor the weak-ref.

In particular, because weak_ref.unref() is not safe to do after
the object was already destroyed. So we need to be correct about
tracking destruction.

https://gitlab.freedesktop.org/NetworkManager/NetworkManager/-/merge_requests/1290

https://gitlab.freedesktop.org/NetworkManager/NetworkManager/-/merge_requests/1247

This is a python example. We should do nice things, like
using max() for finding the maximum, instead of sorting.

"examples/python/gi/checkpoint.py" is not only an example. It's also a
useful script for testing checkpoints.

Support a "--last" argument to specify the last checkpoint created.
Otherwise, when you are using this example from a test script, it
can be cumbersome to find the right checkpoint point.

Also, rename "client" and "nm_client" variables to "nmc". The purpose of
using the same variable name for the same thing is readability, but also
it works better when copy+paste snippets into the Python REPL.

Recent python-black (22.0) dropped support for Python 2 and thus fail
for those files. Make the examples Python3 compatible.

https://gitlab.freedesktop.org/NetworkManager/NetworkManager/-/merge_requests/1043

We use clang-format for automatic formatting of our source files.
Since clang-format is actively maintained software, the actual
formatting depends on the used version of clang-format. That is
unfortunate and painful, but really unavoidable unless clang-format
would be strictly bug-compatible.

So the version that we must use is from the current Fedora release, which
is also tested by our gitlab-ci. Previously, we were using Fedora 34 with
clang-tools-extra-12.0.1-1.fc34.x86_64.

As Fedora 35 comes along, we need to update our formatting as Fedora 35
comes with version "13.0.0~rc1-1.fc35".
An alternative would be to freeze on version 12, but that has different
problems (like, it's cumbersome to rebuild clang 12 on Fedora 35 and it
would be cumbersome for our developers which are on Fedora 35 to use a
clang that they cannot easily install).

The (differently painful) solution is to reformat from time to time, as we
switch to a new Fedora (and thus clang) version.
Usually we would expect that such a reformatting brings minor changes.
But this time, the changes are huge. That is mentioned in the release
notes [1] as

  Makes PointerAligment: Right working with AlignConsecutiveDeclarations. (Fixes https://llvm.org/PR27353)

[1] https://releases.llvm.org/13.0.0/tools/clang/docs/ReleaseNotes.html#clang-format