Swift 4.1にはswift formatとか付いてるのね。
$ TOOLCHAINS=org.swift.4120171025a swift format --help OVERVIEW: Swift Format Tool USAGE: swift [options] <inputs> OPTIONS: -help Display available options -in-place Overwrite input file with formatted file. -indent-switch-case Indent cases in switch statements. -indent-width <n> Number of characters to indent. -line-range <n:n> <start line>:<end line>. Formats a range of lines (1-based). Can only be used with one input file. -o <file> Write output to <file> -tab-width <n> Width of tab character. -use-tabs Use tabs for indentation.