Use clang-format on code

[ksshannon]

I'd like to introduce a requirement for formatting. We can do this automagically using clang-format. Can we agree on a format style? We can write our own, but clang-format has built in formats based on:

• LLVM: a style complying with the LLVM coding standards
• Google: a style complying with Google’s C++ style guide
• Chromium: a style complying with Chromium’s style guide
• Mozilla: A style complying with Mozilla’s style guide
• WebKit A style complying with WebKit’s style guide

It's easiest to just use one of these. I looked at Mozilla, and it looked fine to me. I could care less which one we pick. It is just one less thing we have to think about, and it makes the code predictable.

After one is picked, I'll write a pre-commit hook for git to run it when code is committed, or at least warn when clang-format hasn't been run.

Tasks:

• Pick a format
• Write pre-commit hook
• Add clang-format to dependency scripts and documentation

[ksshannon]

clang-format options:

http://clang.llvm.org/docs/ClangFormatStyleOptions.html

[jforthofer]

Sounds fine to me.

[nwagenbrenner]

Sounds good. Doesn't matter to me which one we use.

[ksshannon]

From http://stackoverflow.com/questions/22866609/can-clang-format-tell-me-if-formatting-changes-are-necessary

git diff --cached --name-only --diff-filter=ACMRT | grep "\.[cmh]$" | xargs -n1 clang-format -style=file -output-replacements-xml | grep "<replacement " >/dev/null
if [ $? -ne 1 ]
then 
    echo "Commit did not match clang-format"
    exit 1;
fi

tell the user the diff does not pass clang format.

[ksshannon]

Install or append scripts/git/pre-commit in the .git/hooks folder. It checks whether or not your commit (not the file) is properly formatted. You can skip it in git commit, but some structure is nice. It's very difficult to read between files, and now that windows is gone from our development for the most part, I think this is a good thing. .clang-format has been installed in the root. It is a straight llvm copy.