Refactor Outdated version logic

Source/carthage/Formatting.swift

@@ -94,35 +94,40 @@ public struct ColorOptions: OptionsProtocol {
 	}
 }
 
-extension OutdatedCommand.UpdateAvailabilityAndApplicability {
-	fileprivate static let dict: [OutdatedCommand.UpdateAvailabilityAndApplicability: Color.Named.Color] = [
-		.updatesAvailableAllApplicable: .green,
-		.updatesAvailableSomeApplicable: .yellow,
-		.updatesAvailableNoneApplicable: .red,
-	]
+extension OutdatedCommand.UpdateType {
+	var color: Color.Named.Color {
+		switch self {
+		case .newest:
+			return .green
+		case .newer:
+			return .yellow
+		case .ineligible:
+			return .red
+		}
+	}
 }
 
 extension ColorOptions.Formatting {
-	subscript(_ index: OutdatedCommand.UpdateAvailabilityAndApplicability) -> Wrap {
-		guard self.isColorful, let color = OutdatedCommand.UpdateAvailabilityAndApplicability.dict[index] else {
+	subscript(_ index: OutdatedCommand.UpdateType?) -> Wrap {
+		guard self.isColorful, let update = index else {
 			return { $0 }
 		}
-		return Color.Wrap(foreground: color).wrap
+		return Color.Wrap(foreground: update.color).wrap
 	}
 
 	public var legendForOutdatedCommand: String? {
 		guard self.isColorful else { return nil }
 
 		let header = "Legend — <color> • «what happens when you run `carthage update`»:\n"
-		return OutdatedCommand.UpdateAvailabilityAndApplicability.dict.reduce(into: header) {
-			let (situation, color) = $1
+		return [OutdatedCommand.UpdateType.newest, .newer, .ineligible].reduce(into: header) {
+			let (color, explanation) = ($1.color, $1.explanation)
 			let tabs = String(
 				repeating: "\t",
 				count: color == .yellow || color == .magenta ? 1 : 2
 			)
 			let colorDescription = Color.Wrap(foreground: color)
 				.wrap("<" + String(describing: color) + ">")
-			$0.append(colorDescription + tabs + "• " + situation.rawValue + "\n")
+			$0.append(colorDescription + tabs + "• " + explanation + "\n")
 		}
 	}
 }

Source/carthage/Outdated.swift

@@ -7,26 +7,30 @@ import Curry
 
 /// Type that encapsulates the configuration and evaluation of the `outdated` subcommand.
 public struct OutdatedCommand: CommandProtocol {
-	enum UpdateAvailabilityAndApplicability: String {
-		case updatesAvailableAllApplicable =
-		"Will be updated to the newest version."
-		case updatesAvailableSomeApplicable =
-		"Will be updated, but not to the newest version because of the specified version in Cartfile."
-		case updatesAvailableNoneApplicable =
-		"Will not be updated because of the specified version in Cartfile."
-		case noUpdatesAvailable =
-		"Will not be updated: no updates available."
+	enum UpdateType {
+		case newest
+		case newer
+		case ineligible
 
-		init(currentVersion current: PinnedVersion, applicableVersion applicable: PinnedVersion, latestVersion latest: PinnedVersion) {
-			switch (current, applicable, latest) {
-			case (current, applicable, latest) where current != latest && applicable == latest:
-				self = .updatesAvailableAllApplicable
-			case (current, applicable, latest) where current != applicable && applicable != latest:
-				self = .updatesAvailableSomeApplicable
-			case (current, applicable, latest) where current != latest && current == applicable:
-				self = .updatesAvailableNoneApplicable
-			default:
-				self = .noUpdatesAvailable
+		init?(currentVersion current: PinnedVersion, applicableVersion applicable: PinnedVersion, latestVersion latest: PinnedVersion) {
+			guard current != latest else { return nil }
+			if applicable == latest {
+				self = .newest
+			} else if current != applicable {
+				self = .newer
+			} else {
+				self = .ineligible
+			}
+		}
+
+		var explanation: String {
+			switch self {
+			case .newest:
+				return "Will be updated to the newest version."
+			case .newer:
+				return "Will be updated, but not to the newest version because of the specified version in Cartfile."
+			case .ineligible:
+				return "Will not be updated because of the specified version in Cartfile."
 			}
 		}
 	}
@@ -83,8 +87,8 @@ public struct OutdatedCommand: CommandProtocol {
 						if options.outputXcodeWarnings {
 							carthage.println("warning: \(formatting.projectName(project.name)) is out of date (\(current) -> \(applicable)) (Latest: \(latest))")
 						} else {
-							let availability = UpdateAvailabilityAndApplicability(currentVersion: current, applicableVersion: applicable, latestVersion: latest)
-							let style = formatting[availability]
+							let update = UpdateType(currentVersion: current, applicableVersion: applicable, latestVersion: latest)
+							let style = formatting[update]
 							let versionSummary = "\(style(current.description)) -> \(style(applicable.description)) (Latest: \(latest))"
 							carthage.println(formatting.projectName(project.name) + " " + versionSummary)
 						}