Add minimum_swiftlint_version as a configuration option

Author: alex-taffe

Source/SwiftLintCore/Extensions/Configuration+Parsing.swift

@@ -9,6 +9,7 @@ extension Configuration {
         case optInRules = "opt_in_rules"
         case reporter = "reporter"
         case swiftlintVersion = "swiftlint_version"
+        case minimumSwiftlintVersion = "minimum_swiftlint_version"
         case warningThreshold = "warning_threshold"
         case onlyRules = "only_rules"
         case indentation = "indentation"
@@ -101,6 +102,7 @@ extension Configuration {
             reporter: dict[Key.reporter.rawValue] as? String ?? XcodeReporter.identifier,
             cachePath: cachePath ?? dict[Key.cachePath.rawValue] as? String,
             pinnedVersion: dict[Key.swiftlintVersion.rawValue].map { ($0 as? String) ?? String(describing: $0) },
+            minimumVersion: dict[Key.minimumSwiftlintVersion.rawValue].map { ($0 as? String) ?? String(describing: $0) },
             allowZeroLintableFiles: dict[Key.allowZeroLintableFiles.rawValue] as? Bool ?? false,
             strict: dict[Key.strict.rawValue] as? Bool ?? false,
             baseline: dict[Key.baseline.rawValue] as? String,

Source/SwiftLintCore/Models/Configuration.swift

@@ -124,7 +124,7 @@ public struct Configuration {
 
     /// Creates a `Configuration` by specifying its properties directly,
     /// except that rules are still to be synthesized from rulesMode, ruleList & allRulesWrapped
-    /// and a check against the pinnedVersion is performed if given.
+    /// and a check against the pinnedVersion/minimumVersion is performed if given.
     ///
     /// - parameter rulesMode:              The `RulesMode` for this configuration.
     /// - parameter allRulesWrapped:        The rules with their own configurations already applied.
@@ -140,6 +140,7 @@ public struct Configuration {
     /// - parameter reporter:               The identifier for the `Reporter` to use to report style violations.
     /// - parameter cachePath:              The location of the persisted cache to use whith this configuration.
     /// - parameter pinnedVersion:          The SwiftLint version defined in this configuration.
+    /// - parameter minimumVersion:         The minimum SwiftLint version defined in this configuration.
     /// - parameter allowZeroLintableFiles: Allow SwiftLint to exit successfully when passed ignored or unlintable
     ///                                     files.
     /// - parameter strict:                 Treat warnings as errors.
@@ -158,6 +159,7 @@ public struct Configuration {
         reporter: String? = nil,
         cachePath: String? = nil,
         pinnedVersion: String? = nil,
+        minimumVersion: String? = nil,
         allowZeroLintableFiles: Bool = false,
         strict: Bool = false,
         baseline: String? = nil,
@@ -171,6 +173,14 @@ public struct Configuration {
             )
             exit(2)
         }
+        
+        if let minimumVersion, minimumVersion.compare(Version.current.value, options: .numeric) == .orderedDescending {
+            queuedPrintError(
+                "warning: Currently running SwiftLint \(Version.current.value) but " +
+                "configuration specified minimum version \(minimumVersion)."
+            )
+            exit(2)
+        }
 
         self.init(
             rulesWrapper: RulesWrapper(