Simplify swift-format soundness script

[simonjbeaumont]

Motivation

The run-swift-format.sh script run as part of soundness explicitly lists the directories to format. This is to avoid running swift-format on the contents of .build/ which contains a checkouts of all the dependencies. This isn't necessary, as we can use Git to tell us what files need to be formatted, which can also make for a more robust script/command as we add new directories.

Additionally, with the previous strategy, Package.swift at the root of the repository was ignored. This was deliberate, but in hindsight I don't think the lack of trailing comma enforcement is worth us excluding it.

Modifications

• Use git ls-files to determine which files need to be passed to swift-format.

Result

• Script is simpler (also easier to add a one-shot command as a pre-commit hook).
• Package.swift is also formatted.

Test Plan

None.

[czechboy0]

Net-negative line count, a simplified script, and more consistent code. What are you, a magician? 🙂💯

[czechboy0]

@swift-server-bot test this please