Tests: use FileManager instead of cp

Rather than relying on UNIX semantics of `cp` which is inherently
platform dependent.  This is required to start experimenting with
getting the SPM test suite running on Windows.

Author: compnerd

IntegrationTests/Tests/IntegrationTests/Helpers.swift

@@ -221,7 +221,8 @@ func fixture(
             if localFileSystem.isFile(fixtureDir.appending(component: "Package.swift")) {
                 // It's a single package, so copy the whole directory as-is.
                 let dstDir = tmpDirPath.appending(component: copyName)
-                try systemQuietly("cp", "-R", "-H", fixtureDir.pathString, dstDir.pathString)
+                try FileManager.default.copyItem(at: URL(fileURLWithPath: fixtureDir.pathString, isDirectory: true),
+                                                 to: URL(fileURLWithPath: dstDir.pathString, isDirectory: true))
 
                 // Invoke the block, passing it the path of the copied fixture.
                 try body(dstDir)
@@ -231,7 +232,8 @@ func fixture(
                     let srcDir = fixtureDir.appending(component: fileName)
                     guard localFileSystem.isDirectory(srcDir) else { continue }
                     let dstDir = tmpDirPath.appending(component: fileName)
-                    try systemQuietly("cp", "-R", "-H", srcDir.pathString, dstDir.pathString)
+                    try FileManager.default.copyItem(at: URL(fileURLWithPath: srcDir.pathString, isDirectory: true),
+                                                     to: URL(fileURLWithPath: dstDir.pathString, isDirectory: true))
                     initGitRepo(dstDir, tag: "1.2.3", addFile: false)
                 }
 

Sources/SPMTestSupport/misc.swift

@@ -11,6 +11,7 @@
 //===----------------------------------------------------------------------===//
 
 import Basics
+import Foundation
 import OrderedCollections
 import PackageGraph
 import PackageLoading
@@ -69,7 +70,8 @@ public func fixture(
             if localFileSystem.isFile(fixtureDir.appending(component: "Package.swift")) {
                 // It's a single package, so copy the whole directory as-is.
                 let dstDir = tmpDirPath.appending(component: copyName)
-                try systemQuietly("cp", "-R", "-H", fixtureDir.pathString, dstDir.pathString)
+                try FileManager.default.copyItem(at: URL(fileURLWithPath: fixtureDir.pathString, isDirectory: true),
+                                                 to: URL(fileURLWithPath: dstDir.pathString, isDirectory: true))
 
                 // Invoke the block, passing it the path of the copied fixture.
                 try body(dstDir)
@@ -79,7 +81,8 @@ public func fixture(
                     let srcDir = fixtureDir.appending(component: fileName)
                     guard localFileSystem.isDirectory(srcDir) else { continue }
                     let dstDir = tmpDirPath.appending(component: fileName)
-                    try systemQuietly("cp", "-R", "-H", srcDir.pathString, dstDir.pathString)
+                    try FileManager.default.copyItem(at: URL(fileURLWithPath: srcDir.pathString, isDirectory: true),
+                                                     to: URL(fileURLWithPath: dstDir.pathString, isDirectory: true))
                     if createGitRepo {
                         initGitRepo(dstDir, tag: "1.2.3", addFile: false)
                     }