Add support for Swift Package Manager

[LinusU]

Benefits:

• Easy to build, run and run tests 🐎
• Usage with Mint (after Parse current OS version as swiftc target yonaskolb/Mint#61)
  • mint run nicklockwood/SwiftFormat

Left to do:

• Figure out why there wasn't an import SwiftFormat in CommandLineTool/main.swift before 🤔 will adding it break anything?
• Maybe update the readme with build and Mint instructions?

What works:

• Building: swift build -Xswiftc -target -Xswiftc x86_64-apple-macosx10.11
• Running tests: swift test -Xswiftc -target -Xswiftc x86_64-apple-macosx10.11

Notes:

• -Xswiftc -target -Xswiftc x86_64-apple-macosx10.11 is added since SwiftPM targets macOS 10.10 by default, and there is currently no way to set it, see:
  • Via Mint <= 0.7.1 or Swift Package Manager 4.X.X without -Xswiftc flag, v0.29.0 can no longer be built Carthage/Carthage#2381
  • Consider passing current platform as target yonaskolb/Mint#58
  • Swift Package Manager macOS deployment target override

All tests passed locally:

Test Suite 'CommandLineTests' passed at 2018-03-28 15:07:51.344.
	 Executed 21 tests, with 0 failures (0 unexpected) in 0.270 (0.271) seconds
Test Suite 'FormatterTests' passed at 2018-03-28 15:07:51.367.
	 Executed 6 tests, with 0 failures (0 unexpected) in 0.023 (0.023) seconds
Test Suite 'OptionsTests' passed at 2018-03-28 15:07:51.422.
	 Executed 52 tests, with 0 failures (0 unexpected) in 0.052 (0.055) seconds
Test Suite 'PerformanceTests' passed at 2018-03-28 15:23:35.086.
	 Executed 10 tests, with 0 failures (0 unexpected) in 943.663 (943.663) seconds
Test Suite 'RulesTests' passed at 2018-03-28 15:23:38.563.
	 Executed 778 tests, with 0 failures (0 unexpected) in 3.381 (3.477) seconds
Test Suite 'SwiftFormatTests' passed at 2018-03-28 15:23:38.592.
	 Executed 12 tests, with 0 failures (0 unexpected) in 0.027 (0.028) seconds
Test Suite 'TokenizerTests' passed at 2018-03-28 15:23:38.683.
	 Executed 200 tests, with 0 failures (0 unexpected) in 0.079 (0.091) seconds
Test Suite 'SwiftFormatPackageTests.xctest' passed at 2018-03-28 15:23:38.683.
	 Executed 1079 tests, with 0 failures (0 unexpected) in 947.494 (947.611) seconds
Test Suite 'All tests' passed at 2018-03-28 15:23:38.684.
	 Executed 1079 tests, with 0 failures (0 unexpected) in 947.494 (947.612) seconds

[coveralls]

Coverage decreased (-0.002%) to 83.802% when pulling 4612ba3 on LinusU:swiftpm into a00d6fc on nicklockwood:master.

[yonaskolb]

Duplicate of #183

[LinusU]

Haha 🤦‍♂️, seems like I was a bit eager here...

[yonaskolb]

No, it's good. I've love for one of these to get merged

[LinusU]

Yeah, me too! Ping @nicklockwood

[yonaskolb]

I think this is actually more up to date 👍
@LinusU you should open it again

[yonaskolb]

Actually just updated my branch