Proposed clang-format Config

[insertinterestingnamehere]

I'd like to start using clang-format to manage formatting. As far as I can tell, the formatting isn't especially consistent across the codebase right now. Here's an initial config based on my own preferences that we can use as a starting point. Feel free to suggest any changes.

I'll leave this open for a while to give time for any comments. Once we've settled on a format spec to use, I'll set things up to exclude any vendored files, apply the format to the whole codebase whenever there aren't open pull requests, then set up a CI build to check that the formatting has been correctly applied to each pull request.

[janciesko]

I am ok using clang-format.

[janciesko]

You can also reuse this config file, for consistency across code bases. https://github.com/kokkos/kokkos/blob/master/.clang-format

[insertinterestingnamehere]

Yah, I'm fine with mimicking their config too if that's preferable. I don't think it's quite possible to maintain perfect reuse because of options that tag the behavior of specific macros. AttributeMacros is the only one like that that we'll currently want to use, but others could really easily become needed too (for example for warning suppression macros). We can do things mostly the same though.

The main nontrivial differences between my proposed file and theirs is that they set AlignConsecutiveAssignments: true, that I enforce header alphabetizing inside blocks, and that I set QualifierAlignment to follow the "east const" convention instead of leaving it inconsistent. We can also enforce "west const" instead if we want.

There are also some places where the default BreakArrays setting will make some things look a little silly, but they're fairly rare.

I think InsertNewlineAtEOF: true can make diffs slightly less cluttered because of some weirdness with how git handles newlines on Windows and also different editor configs, but I haven't confirmed that.

[janciesko]

LGTM