The commit style checker had a hard-coded assumption that the changes
were made against the master branch. For backports that is not the case
though and that's why the script fails for backports as soon as the
master and the backport branch have diverged.
This new check will fail if there is a c++ source code file that is not
formatted according to our project's formatting standards (specified via
.clang-format file).
Tests that require an active internet connection will now be omitted on
CI as they recently caused a bunch of CI jobs to fail just because some
external server was unreachable.
Now that Travis CI decided to stop offering their services for free, we
had to look for an alternative solution. GitHub Actions seems to fit the
picture really well and has the benefit of being tightly integrated into
GitHub (obviously).
For now only shared builds for Ubuntu 18.04 and 20.04 are included. The
scripts and the framework for also including static builds is part of
this commit as well but as it stands the static build always failed and
therefore it was given up upon for now.
Adding support for other OS will require a few tweaks and a couple of
new scripts but in general the framework was built with this kind of
extension in mind.
