add .clang-format

[mr-martian]

In which I am mildly opinionated about C++ code formatting.

Not sure if this should go here and get copied to all the other repos or if there's somewhere else it should go.

Anyway, I'm sure someone will disagree with at least one of these settings, so let the bikeshedding begin. :)

Explanation of options: https://clang.llvm.org/docs/ClangFormatStyleOptions.html (I couldn't figure out how to get newer than 10.0 via apt, so I'm ignoring options from more recent versions.)

Version 10 manual: https://releases.llvm.org/10.0.0/tools/clang/docs/ClangFormatStyleOptions.html
Working interactive configurator: https://clang-format-configurator.site/

[mr-martian]

This was previously suggested in apertium/apertium-lex-tools#84 and while there are still several open PRs, most of them are mine and have a fair amount of changes that need to be integrated anyway.

[TinoDidriksen]

Committed my opinion. In particular:

• AlignConsecutiveAssignments: true is fundamentally a good idea, but clang-format makes so many mistakes. But with false then it mangles existing manual alignments. Not sure which is the best default - probably true but then other changes are needed.
• clang-format mangles preprocessor directives regardless of what options or versions used. It has no way to simply leave them alone.
• I very strongly want breaks before else and catch - Egyptian braces makes moving code around so much easier.
• ColumnLimit: 0 because IDEs will show very long lines broken with proper indentation. There is no reason to bake in such breaks any longer. We're well past the days of teletype terminals.

I "solved" similar issues in CG-3 with https://github.com/GrammarSoft/cg3/blob/main/scripts/clang-format.pl

[flammie]

• ColumnLimit: 0 because IDEs will show very long lines broken with proper indentation. There is no reason to bake in such breaks any longer. We're well past the days of teletype terminals.

I have no bikeshed hills to die on in code formatting issues, but I do have a strong opinion on this, long lines are really unreadable in 90 % of editors, ides (though suggestions for good such visualisations for vim and emacs are welcome) but also diff formats on console or web. Using more than 80 characters in a reasonable (non-java non-xml) language is almost always a sign of a really badly structured code.

[TinoDidriksen]

Using more than 80 characters in a reasonable (non-java non-xml) language is almost always a sign of a really badly structured code.

My usual compromise is 120 characters. 80 is just too damn small, imo.