[Development] Proposal: (re)move qt5.git/_clang-format

[Marc Mutz]

Hi,

TL;DR:
- remove _clang-format in qt5.git
- add it instead to submodules which conform to it

The clang-format philosophy is that you pick a config and stick to it. 
If your personal preferences are different, you use a different 
configuration locally and re-format on check-in and check-out.

This means that the source code in the VCS must always conform to the 
clang-format configuration in effect in that branch. It also means that 
when and if you make changes to the clang-format configuration, you need 
to re-run the tool over the whole code base and apply the changed 
configuration, otherwise the clang-format workflow doesn't work 
(produces unrelated white-space changes).

We have for quite some time had a _clang-format config file in qt5.git. 
After many attempts by many people, it has become clear that a) it has 
completely wrong settings (e.g. template<> vs. template <>), leading to 
a complete formatting mess in modules that predate the addition of the 
file and more discussions around formatting than before, because there 
appear to be two true styles, and b) we can't seem to hammer 
clang-format into reproducing what we traditionally understand as the Qt 
style. In addition, the position in qt5.git means that if you edit files 
in submodules of qt5.git, the config is in effect, if you just checkout 
qtbase, it is not.

I would therefore propose to remove the file from qt5.git:
https://codereview.qt-project.org/c/qt/qt5/+/503430

Newer submodules which have been developed against and therefore adhere 
to the file should feel free to add it to the submodule, but it 
shouldn't be in qt5.git anymore. They should also make sure that they're 
up-to-date with any changes that have been made to _clang-format over 
the time (or revert them in their copy), and get clang-format nagging 
enabled in the CI.

WDYT?

Thanks,
Marc

-- 
Marc Mutz <marc.mutz at qt.io>
Principal Software Engineer

The Qt Company
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