Update comments and reduce the diff

Author: MaxDesiatov

Sources/PackageGraph/Resolution/ResolvedTarget.swift

@@ -2,7 +2,7 @@
 //
 // This source file is part of the Swift open source project
 //
-// Copyright (c) 2014-2020 Apple Inc. and the Swift project authors
+// Copyright (c) 2014-2023 Apple Inc. and the Swift project authors
 // Licensed under Apache License v2.0 with Runtime Library Exception
 //
 // See http://swift.org/LICENSE.txt for license information

Sources/PackageLoading/PackageBuilder.swift

@@ -2,7 +2,7 @@
 //
 // This source file is part of the Swift open source project
 //
-// Copyright (c) 2014-2021 Apple Inc. and the Swift project authors
+// Copyright (c) 2014-2023 Apple Inc. and the Swift project authors
 // Licensed under Apache License v2.0 with Runtime Library Exception
 //
 // See http://swift.org/LICENSE.txt for license information

Sources/PackageModel/BuildSettings.swift

@@ -2,7 +2,7 @@
 //
 // This source file is part of the Swift open source project
 //
-// Copyright (c) 2014-2018 Apple Inc. and the Swift project authors
+// Copyright (c) 2014-2023 Apple Inc. and the Swift project authors
 // Licensed under Apache License v2.0 with Runtime Library Exception
 //
 // See http://swift.org/LICENSE.txt for license information
@@ -43,6 +43,7 @@ public enum BuildSettings {
         /// The assignment value.
         public var values: [String]
 
+        // FIXME: This should use `Set` but we need to investigate potential build failures on Linux caused by using it.
         /// The condition associated with this assignment.
         public var conditions: [PackageCondition] {
             get {
@@ -71,6 +72,7 @@ public enum BuildSettings {
 
         /// Add the given assignment to the table.
         mutating public func add(_ assignment: Assignment, for decl: Declaration) {
+            // FIXME: We should check for duplicate assignments.
             assignments[decl, default: []].append(assignment)
         }
     }

Sources/SPMBuildCore/Plugins/PluginInvocation.swift

@@ -2,7 +2,7 @@
 //
 // This source file is part of the Swift open source project
 //
-// Copyright (c) 2021-2022 Apple Inc. and the Swift project authors
+// Copyright (c) 2021-2023 Apple Inc. and the Swift project authors
 // Licensed under Apache License v2.0 with Runtime Library Exception
 //
 // See http://swift.org/LICENSE.txt for license information

Sources/XCBuildSupport/PIF.swift

@@ -2,7 +2,7 @@
 //
 // This source file is part of the Swift open source project
 //
-// Copyright (c) 2014-2020 Apple Inc. and the Swift project authors
+// Copyright (c) 2014-2023 Apple Inc. and the Swift project authors
 // Licensed under Apache License v2.0 with Runtime Library Exception
 //
 // See http://swift.org/LICENSE.txt for license information

Sources/XCBuildSupport/PIFBuilder.swift

@@ -2,7 +2,7 @@
 //
 // This source file is part of the Swift open source project
 //
-// Copyright (c) 2014-2021 Apple Inc. and the Swift project authors
+// Copyright (c) 2014-2023 Apple Inc. and the Swift project authors
 // Licensed under Apache License v2.0 with Runtime Library Exception
 //
 // See http://swift.org/LICENSE.txt for license information

Tests/PackageLoadingTests/PackageBuilderTests.swift

@@ -2,7 +2,7 @@
 //
 // This source file is part of the Swift open source project
 //
-// Copyright (c) 2014-2021 Apple Inc. and the Swift project authors
+// Copyright (c) 2014-2023 Apple Inc. and the Swift project authors
 // Licensed under Apache License v2.0 with Runtime Library Exception
 //
 // See http://swift.org/LICENSE.txt for license information
@@ -19,8 +19,7 @@ import XCTest
 import class TSCBasic.InMemoryFileSystem
 
 /// Tests for the handling of source layout conventions.
-class PackageBuilderTests: XCTestCase {
-
+final class PackageBuilderTests: XCTestCase {
     func testDotFilesAreIgnored() throws {
         let fs = InMemoryFileSystem(emptyFiles:
             "/Sources/foo/.Bar.swift",