clang-format: Set PackConstructorInitializers: CurrentLine

[maflcko]

Now that the minimum supported clang version is larger than 14, the PackConstructorInitializers setting can be set to CurrentLine in the clang-format file. (This option was added in clang 14. Ref: https://releases.llvm.org/17.0.1/tools/clang/docs/ClangFormatStyleOptions.html#packconstructorinitializers)

The CurrentLine option will either put all constructor initializers on the current line if they fit. Otherwise, it will put each one on its own line.

The CurrentLine option is desirable over the current BinPack option, because:

• It is what the majority of the codebase is currently using.
• It makes it easier to skim the lines to ensure all fields are properly initialized, without having to parse bin-packed constructor initializers, possibly with nested initializer lists, function calls, or ternary operators.
• It makes diffs smaller when an initializer is added or removed, because only a single line is touched. Otherwise, the whole bin-packed block could re-flow, making the diff harder to parse.

Note: The previous BinPack option allows any formatting, due to the current ColumnLimit: 0. I presume developers manually formatted most constructor initializers to be on separate lines? With the new CurrentLine setting, one has to only put the first initializer on a separate line, and clang-format will take care of the rest.

For example:

echo 'A::A(O o)
: m_first{o.a, o.b},
  m_second{fun(o)}, m_third{o.c?o.d:o.e} {}' | clang-format --style=file:./src/.clang-format

Will put each on a separate line. Previously, it was left as-is.

[DrahtBot]

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ACK	l0rinc, TheCharlatan, hebasto

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[l0rinc]

ACK fad0c76

I agree that this is our best option now, mostly because it will minimize diffs without blowing up line-count for trivial ones

[sedited]

ACK fad0c76

[hebasto]

ACK fad0c76.