Trying out Google's swift-format. Build with:
git clone -b swift-5.2-branch https://github.com/apple/swift-format.git
cd swift-format
swift build
.build/x86_64-apple-macosx/debug/swift-format --help
OVERVIEW: Format or lint Swift source code.
USAGE: swift-format [options] <filename or path> ...
OPTIONS:
--configuration The path to a JSON file containing the configuration of the linter/formatter.
--in-place, -i Overwrite the current file when formatting ('format' mode only).
--mode, -m The mode to run swift-format in. Either 'format', 'lint', or 'dump-configuration'.
--recursive, -r Recursively run on '.swift' files in any provided directories.
--version, -v Prints the version and exists
--help Display available options
POSITIONAL ARGUMENTS:
filenames or paths One or more input filenames
UPDATE: Now uses swift-5.2-branch (for Xcode 11.4), according to Matching swift-format to Your Swift Version.