Moved XIP expansion to a temporal directory

Instead of expanding XIPs on its current directory, a temporal directory is used. The main advantage of this approach is that, because the temporal directory is created on the same volume where Xcode will be installed, the installation is vastly improved if the XIP is on a different volume.

- https://nshipster.com/temporary-files/
- The implementation of the `temporalDirectory` function and variable are based on the similar `trashItem`, but without the `@discardableResult` annotation (I cannot think of any case where this URL could to be ignored).

This closes #178.

Sources/XcodesKit/Environment.swift

@@ -23,7 +23,7 @@ public struct Environment {
 public var Current = Environment()
 
 public struct Shell {
-    public var unxip: (URL) -> Promise<ProcessOutput> = { Process.run(Path.root.usr.bin.xip, workingDirectory: $0.deletingLastPathComponent(), "--expand", "\($0.path)") }
+    public var unxip: (URL, URL) -> Promise<ProcessOutput> = { Process.run(Path.root.usr.bin.xip, workingDirectory: $1, "--expand", "\($0.path)") }
     public var spctlAssess: (URL) -> Promise<ProcessOutput> = { Process.run(Path.root.usr.sbin.spctl, "--assess", "--verbose", "--type", "execute", "\($0.path)") }
     public var codesignVerify: (URL) -> Promise<ProcessOutput> = { Process.run(Path.root.usr.bin.codesign, "-vv", "-d", "\($0.path)") }
     public var devToolsSecurityEnable: (String?) -> Promise<ProcessOutput> = { Process.sudo(password: $0, Path.root.usr.sbin.DevToolsSecurity, "-enable") }
@@ -238,6 +238,12 @@ public struct Files {
         try createDirectory(url, createIntermediates, attributes)
     }
 
+    public var temporalDirectory: (URL) throws -> URL = { try FileManager.default.url(for: .itemReplacementDirectory, in: .userDomainMask, appropriateFor: $0, create: true) }
+
+    public func temporalDirectory(for URL: URL) throws -> URL {
+        return try temporalDirectory(URL)
+    }
+
     public var installedXcodes = XcodesKit.installedXcodes
 }
 private func installedXcodes(directory: Path) -> [InstalledXcode] {

Sources/XcodesKit/XcodeInstaller.swift

@@ -718,9 +718,10 @@ public final class XcodeInstaller {
     }
 
     func unarchiveAndMoveXIP(at source: URL, to destination: URL) -> Promise<URL> {
+        let xcodeExpansionDirectory = (try? Current.files.temporalDirectory(for: destination)) ?? source.deletingLastPathComponent()
         return firstly { () -> Promise<ProcessOutput> in
             Current.logging.log(InstallationStep.unarchiving.description)
-            return Current.shell.unxip(source)
+            return Current.shell.unxip(source, xcodeExpansionDirectory)
                 .recover { (error) throws -> Promise<ProcessOutput> in
                     if case Process.PMKError.execution(_, _, let standardError) = error,
                        standardError?.contains("damaged and can’t be expanded") == true {
@@ -732,8 +733,8 @@ public final class XcodeInstaller {
         .map { output -> URL in
             Current.logging.log(InstallationStep.moving(destination: destination.path).description)
 
-            let xcodeURL = source.deletingLastPathComponent().appendingPathComponent("Xcode.app")
-            let xcodeBetaURL = source.deletingLastPathComponent().appendingPathComponent("Xcode-beta.app")
+            let xcodeURL = xcodeExpansionDirectory.appendingPathComponent("Xcode.app")
+            let xcodeBetaURL = xcodeExpansionDirectory.appendingPathComponent("Xcode-beta.app")
             if Current.files.fileExists(atPath: xcodeURL.path) {
                 try Current.files.moveItem(at: xcodeURL, to: destination)
             }

Tests/XcodesKitTests/Environment+Mock.swift

@@ -16,7 +16,7 @@ extension Shell {
     static var processOutputMock: ProcessOutput = (0, "", "")
 
     static var mock = Shell(
-        unxip: { _ in return Promise.value(Shell.processOutputMock) },
+        unxip: { _, _ in return Promise.value(Shell.processOutputMock) },
         spctlAssess: { _ in return Promise.value(Shell.processOutputMock) },
         codesignVerify: { _ in return Promise.value(Shell.processOutputMock) },
         devToolsSecurityEnable: { _ in return Promise.value(Shell.processOutputMock) },
@@ -60,6 +60,7 @@ extension Files {
         trashItem: { _ in return URL(fileURLWithPath: "\(NSHomeDirectory())/.Trash") },
         createFile: { _, _, _ in return true },
         createDirectory: { _, _, _ in },
+        temporalDirectory: { _ in return URL(fileURLWithPath: NSTemporaryDirectory()) },
         installedXcodes: { _ in [] }
     )
 }

Tests/XcodesKitTests/XcodesKitTests.swift

@@ -707,7 +707,7 @@ final class XcodesKitTests: XCTestCase {
             XcodesKit.Current.logging.log(prompt)
             return "asdf"
         }
-        Current.shell.unxip = { _ in 
+        Current.shell.unxip = { _, _ in 
             unxipCallCount += 1
             if unxipCallCount == 1 {
                 return Promise(error: Process.PMKError.execution(process: Process(), standardOutput: nil, standardError: "The file \"Xcode-0.0.0.xip\" is damaged and can’t be expanded."))