Re: Add a tentative .clang-format for LilyPond. (issue 561340043 by address@hidden)

[nine . fierce . ballads]

I'm running some of my patches through clang-format as I prepare to push
them.

This is an example of a kind of change it wants to make:

-  const array<int, 2> key {column_rank, dir};
+  const array<int, 2> key{column_rank, dir};

Note the space after key.  The setting that controls this is
SpaceBeforeCpp11BracedList.  Am I correct that we should use a space
here for consistency with historical style?

More examples of the effect of the option are in the docs:
https://releases.llvm.org/9.0.0/tools/clang/docs/ClangFormatStyleOptions.html

https://codereview.appspot.com/561340043/