Add --style to select the formatting style

[hferreiro]

--aosp was the only style switch, with no way to select Google Style once it had been passed. Wrapper scripts such as Chromium's google-java-format launcher append --aosp unconditionally, leaving projects that format through them no way to opt back into Google Style.

Add a --style=<google|aosp> flag, and allow overriding a previously given style. --aosp is kept as an alias for --style=aosp.

[cushon]

Thanks, this looks fine.

One minor question: WDYT about --google-style or something like that instead of --no-aosp? I don't think we're expecting to add more styles here, and the behaviour would be the same, I just wonder if it's slightly clearer.

[hferreiro]

Hey @cushon, what do you think about the latest update? I followed clang-format and added a --style= flag instead, while keeping --aosp for backwards compatibility.

I'll go with --google-style if that's preferred.