diff --git a/src/Pure/System/cygwin.scala b/src/Pure/System/cygwin.scala
--- a/src/Pure/System/cygwin.scala
+++ b/src/Pure/System/cygwin.scala
@@ -1,65 +1,18 @@
 /*  Title:      Pure/System/cygwin.scala
     Author:     Makarius
 
 Cygwin as POSIX emulation on Windows.
 */
 
 package isabelle
 
 
 import java.io.{File => JFile}
 import java.nio.file.Files
 
 import scala.annotation.tailrec
 
 
 object Cygwin
 {
-  /* init (e.g. after extraction via 7zip) */
-
-  def init(isabelle_root: String, cygwin_root: String): Unit =
-  {
-    require(Platform.is_windows, "Windows platform expected")
-
-    def exec(cmdline: String*): Unit =
-    {
-      val cwd = new JFile(isabelle_root)
-      val env = sys.env + ("CYGWIN" -> "nodosfilewarning")
-      val proc = Isabelle_Env.process(cmdline.toList, cwd = cwd, env = env, redirect = true)
-      val (output, rc) = Isabelle_Env.process_output(proc)
-      if (rc != 0) error(output)
-    }
-
-    val uninitialized_file = new JFile(cygwin_root, "isabelle\\uninitialized")
-    val uninitialized = uninitialized_file.isFile && uninitialized_file.delete
-
-    if (uninitialized) {
-      val symlinks =
-      {
-        val path = (new JFile(cygwin_root + "\\isabelle\\symlinks")).toPath
-        Files.readAllLines(path, UTF8.charset).toArray.toList.asInstanceOf[List[String]]
-      }
-      @tailrec def recover_symlinks(list: List[String]): Unit =
-      {
-        list match {
-          case Nil | List("") =>
-          case target :: content :: rest =>
-            link(content, new JFile(isabelle_root, target))
-            recover_symlinks(rest)
-          case _ => error("Unbalanced symlinks list")
-        }
-      }
-      recover_symlinks(symlinks)
-
-      exec(cygwin_root + "\\bin\\dash.exe", "/isabelle/rebaseall")
-      exec(cygwin_root + "\\bin\\bash.exe", "/isabelle/postinstall")
-    }
-  }
-
-  def link(content: String, target: JFile): Unit =
-  {
-    val target_path = target.toPath
-    Files.writeString(target_path, "!<symlink>" + content + "\u0000")
-    Files.setAttribute(target_path, "dos:system", true)
-  }
 }
diff --git a/src/Pure/System/isabelle_env.scala b/src/Pure/System/isabelle_env.scala
--- a/src/Pure/System/isabelle_env.scala
+++ b/src/Pure/System/isabelle_env.scala
@@ -1,171 +1,227 @@
 /*  Title:      Pure/System/isabelle_env.scala
     Author:     Makarius
 
 Fundamental Isabelle system environment: quasi-static module with
 optional init operation.
 */
 
 package isabelle
 
 
 import java.io.{File => JFile}
+import java.nio.file.Files
 
 import scala.jdk.CollectionConverters._
-
+import scala.annotation.tailrec
 
 
 object Isabelle_Env
 {
   /** bootstrap information **/
 
   def jdk_home(): String =
   {
     val java_home = System.getProperty("java.home", "")
     val home = new JFile(java_home)
     val parent = home.getParent
     if (home.getName == "jre" && parent != null &&
         (new JFile(new JFile(parent, "bin"), "javac")).exists) parent
     else java_home
   }
 
   def bootstrap_directory(
     preference: String, envar: String, property: String, description: String): String =
   {
     val value =
       proper_string(preference) orElse  // explicit argument
       proper_string(System.getenv(envar)) orElse  // e.g. inherited from running isabelle tool
       proper_string(System.getProperty(property)) getOrElse  // e.g. via JVM application boot process
       error("Unknown " + description + " directory")
 
     if ((new JFile(value)).isDirectory) value
     else error("Bad " + description + " directory " + quote(value))
   }
 
 
 
+  /** Support for Cygwin as POSIX emulation on Windows **/
+
+  /* symlink emulation */
+
+  def cygwin_link(content: String, target: JFile): Unit =
+  {
+    val target_path = target.toPath
+    Files.writeString(target_path, "!<symlink>" + content + "\u0000")
+    Files.setAttribute(target_path, "dos:system", true)
+  }
+
+
+  /* init (e.g. after extraction via 7zip) */
+
+  def cygwin_init(isabelle_root: String, cygwin_root: String): Unit =
+  {
+    require(Platform.is_windows, "Windows platform expected")
+
+    def exec(cmdline: String*): Unit =
+    {
+      val cwd = new JFile(isabelle_root)
+      val env = sys.env + ("CYGWIN" -> "nodosfilewarning")
+      val proc = Isabelle_Env.process(cmdline.toList, cwd = cwd, env = env, redirect = true)
+      val (output, rc) = Isabelle_Env.process_output(proc)
+      if (rc != 0) error(output)
+    }
+
+    val uninitialized_file = new JFile(cygwin_root, "isabelle\\uninitialized")
+    val uninitialized = uninitialized_file.isFile && uninitialized_file.delete
+
+    if (uninitialized) {
+      val symlinks =
+      {
+        val path = (new JFile(cygwin_root + "\\isabelle\\symlinks")).toPath
+        Files.readAllLines(path, UTF8.charset).toArray.toList.asInstanceOf[List[String]]
+      }
+      @tailrec def recover_symlinks(list: List[String]): Unit =
+      {
+        list match {
+          case Nil | List("") =>
+          case target :: content :: rest =>
+            cygwin_link(content, new JFile(isabelle_root, target))
+            recover_symlinks(rest)
+          case _ => error("Unbalanced symlinks list")
+        }
+      }
+      recover_symlinks(symlinks)
+
+      exec(cygwin_root + "\\bin\\dash.exe", "/isabelle/rebaseall")
+      exec(cygwin_root + "\\bin\\bash.exe", "/isabelle/postinstall")
+    }
+  }
+
+
+
   /** raw process **/
 
   /* raw process */
 
   def process(command_line: List[String],
     cwd: JFile = null,
     env: Map[String, String] = settings(),
     redirect: Boolean = false): Process =
   {
     val proc = new ProcessBuilder
 
     // fragile on Windows:
     // see https://docs.microsoft.com/en-us/cpp/cpp/main-function-command-line-args?view=msvc-160
     proc.command(command_line.asJava)
 
     if (cwd != null) proc.directory(cwd)
     if (env != null) {
       proc.environment.clear()
       for ((x, y) <- env) proc.environment.put(x, y)
     }
     proc.redirectErrorStream(redirect)
     proc.start
   }
 
   def process_output(proc: Process): (String, Int) =
   {
     proc.getOutputStream.close()
 
     val output = File.read_stream(proc.getInputStream)
     val rc =
       try { proc.waitFor }
       finally {
         proc.getInputStream.close()
         proc.getErrorStream.close()
         proc.destroy()
         Exn.Interrupt.dispose()
       }
     (output, rc)
   }
 
 
 
   /** implicit settings environment **/
 
   @volatile private var _settings: Option[Map[String, String]] = None
 
   def settings(): Map[String, String] =
   {
     if (_settings.isEmpty) init("", "")  // unsynchronized check
     _settings.get
   }
 
   def init(isabelle_root: String, cygwin_root: String): Unit = synchronized
   {
     if (_settings.isEmpty) {
       val isabelle_root1 =
         bootstrap_directory(isabelle_root, "ISABELLE_ROOT", "isabelle.root", "Isabelle root")
 
       val cygwin_root1 =
         if (Platform.is_windows)
           bootstrap_directory(cygwin_root, "CYGWIN_ROOT", "cygwin.root", "Cygwin root")
         else ""
 
-      if (Platform.is_windows) Cygwin.init(isabelle_root1, cygwin_root1)
+      if (Platform.is_windows) cygwin_init(isabelle_root1, cygwin_root1)
 
       def set_cygwin_root(): Unit =
       {
         if (Platform.is_windows)
           _settings = Some(_settings.getOrElse(Map.empty) + ("CYGWIN_ROOT" -> cygwin_root1))
       }
 
       set_cygwin_root()
 
       def default(env: Map[String, String], entry: (String, String)): Map[String, String] =
         if (env.isDefinedAt(entry._1) || entry._2 == "") env
         else env + entry
 
       val env =
       {
         val temp_windows =
         {
           val temp = if (Platform.is_windows) System.getenv("TEMP") else null
           if (temp != null && temp.contains('\\')) temp else ""
         }
         val user_home = System.getProperty("user.home", "")
         val isabelle_app = System.getProperty("isabelle.app", "")
 
         default(
           default(
             default(sys.env + ("ISABELLE_JDK_HOME" -> File.standard_path(jdk_home())),
               "TEMP_WINDOWS" -> temp_windows),
             "HOME" -> user_home),
           "ISABELLE_APP" -> isabelle_app)
       }
 
       val settings =
       {
         val dump = JFile.createTempFile("settings", null)
         dump.deleteOnExit
         try {
           val cmd1 =
             if (Platform.is_windows)
               List(cygwin_root1 + "\\bin\\bash", "-l",
                 File.standard_path(isabelle_root1 + "\\bin\\isabelle"))
             else
               List(isabelle_root1 + "/bin/isabelle")
           val cmd = cmd1 ::: List("getenv", "-d", dump.toString)
 
           val (output, rc) = process_output(process(cmd, env = env, redirect = true))
           if (rc != 0) error(output)
 
           val entries =
             space_explode('\u0000', File.read(dump)).flatMap(
               {
                 case Properties.Eq(a, b) => Some(a -> b)
                 case s => if (s.isEmpty || s.startsWith("=")) None else Some(s -> "")
               }).toMap
           entries + ("PATH" -> entries("PATH_JVM")) - "PATH_JVM"
         }
         finally { dump.delete }
       }
       _settings = Some(settings)
       set_cygwin_root()
     }
   }
 }
diff --git a/src/Pure/System/isabelle_system.scala b/src/Pure/System/isabelle_system.scala
--- a/src/Pure/System/isabelle_system.scala
+++ b/src/Pure/System/isabelle_system.scala
@@ -1,478 +1,479 @@
 /*  Title:      Pure/System/isabelle_system.scala
     Author:     Makarius
 
 Miscellaneous Isabelle system operations.
 */
 
 package isabelle
 
 
 import java.io.{File => JFile, IOException}
 import java.nio.file.{Path => JPath, Files, SimpleFileVisitor, FileVisitResult,
   StandardCopyOption, FileSystemException}
 import java.nio.file.attribute.BasicFileAttributes
 
 
 object Isabelle_System
 {
   /* settings */
 
   def settings(): Map[String, String] = Isabelle_Env.settings()
 
   def getenv(name: String, env: Map[String, String] = settings()): String =
     env.getOrElse(name, "")
 
   def getenv_strict(name: String, env: Map[String, String] = settings()): String =
     proper_string(getenv(name, env)) getOrElse
       error("Undefined Isabelle environment variable: " + quote(name))
 
   def cygwin_root(): String = getenv_strict("CYGWIN_ROOT")
 
 
   /* services */
 
   abstract class Service
 
   @volatile private var _services: Option[List[Class[Service]]] = None
 
   def services(): List[Class[Service]] =
   {
     if (_services.isEmpty) init()  // unsynchronized check
     _services.get
   }
 
   def make_services[C](c: Class[C]): List[C] =
     for { c1 <- services() if Library.is_subclass(c1, c) }
       yield c1.getDeclaredConstructor().newInstance().asInstanceOf[C]
 
 
   /* init settings + services */
 
   def init(isabelle_root: String = "", cygwin_root: String = ""): Unit =
   {
     Isabelle_Env.init(isabelle_root, cygwin_root)
     synchronized {
       if (_services.isEmpty) {
         val variable = "ISABELLE_SCALA_SERVICES"
         val services =
           for (name <- space_explode(':', getenv_strict(variable)))
             yield {
               def err(msg: String): Nothing =
                 error("Bad entry " + quote(name) + " in " + variable + "\n" + msg)
               try { Class.forName(name).asInstanceOf[Class[Service]] }
               catch {
                 case _: ClassNotFoundException => err("Class not found")
                 case exn: Throwable => err(Exn.message(exn))
               }
             }
         _services = Some(services)
       }
     }
   }
 
 
   /* getetc -- static distribution parameters */
 
   def getetc(name: String, root: Path = Path.ISABELLE_HOME): Option[String] =
   {
     val path = root + Path.basic("etc") + Path.basic(name)
     if (path.is_file) {
       Library.trim_split_lines(File.read(path)) match {
         case Nil => None
         case List(s) => Some(s)
         case _ => error("Single line expected in " + path.absolute)
       }
     }
     else None
   }
 
 
   /* Isabelle distribution identification */
 
   def isabelle_id(root: Path = Path.ISABELLE_HOME): String =
     getetc("ISABELLE_ID", root = root) orElse Mercurial.archive_id(root) getOrElse {
       if (Mercurial.is_repository(root)) Mercurial.repository(root).parent()
       else error("Failed to identify Isabelle distribution " + root)
     }
 
   object Isabelle_Id extends Scala.Fun_String("isabelle_id")
   {
     val here = Scala_Project.here
     def apply(arg: String): String = isabelle_id()
   }
 
   def isabelle_tags(root: Path = Path.ISABELLE_HOME): String =
     getetc("ISABELLE_TAGS", root = root) orElse Mercurial.archive_tags(root) getOrElse {
       if (Mercurial.is_repository(root)) {
         val hg = Mercurial.repository(root)
         hg.tags(rev = hg.parent())
       }
       else ""
     }
 
   def isabelle_identifier(): Option[String] = proper_string(getenv("ISABELLE_IDENTIFIER"))
 
   def isabelle_heading(): String =
     isabelle_identifier() match {
       case None => ""
       case Some(version) => " (" + version + ")"
     }
 
   def isabelle_name(): String = getenv_strict("ISABELLE_NAME")
 
   def identification(): String = "Isabelle/" + isabelle_id() + isabelle_heading()
 
 
   /** file-system operations **/
 
   /* scala functions */
 
   private def apply_paths(args: List[String], fun: List[Path] => Unit): List[String] =
     { fun(args.map(Path.explode)); Nil }
 
   private def apply_paths1(args: List[String], fun: Path => Unit): List[String] =
     apply_paths(args, { case List(path) => fun(path) })
 
   private def apply_paths2(args: List[String], fun: (Path, Path) => Unit): List[String] =
     apply_paths(args, { case List(path1, path2) => fun(path1, path2) })
 
   private def apply_paths3(args: List[String], fun: (Path, Path, Path) => Unit): List[String] =
     apply_paths(args, { case List(path1, path2, path3) => fun(path1, path2, path3) })
 
 
   /* permissions */
 
   def chmod(arg: String, path: Path): Unit =
     bash("chmod " + arg + " " + File.bash_path(path)).check
 
   def chown(arg: String, path: Path): Unit =
     bash("chown " + arg + " " + File.bash_path(path)).check
 
 
   /* directories */
 
   def make_directory(path: Path): Path =
   {
     if (!path.is_dir) {
       try { Files.createDirectories(path.file.toPath) }
       catch { case ERROR(_) => error("Failed to create directory: " + path.absolute) }
     }
     path
   }
 
   def new_directory(path: Path): Path =
     if (path.is_dir) error("Directory already exists: " + path.absolute)
     else make_directory(path)
 
   def copy_dir(dir1: Path, dir2: Path): Unit =
   {
     val res = bash("cp -a " + File.bash_path(dir1) + " " + File.bash_path(dir2))
     if (!res.ok) {
       cat_error("Failed to copy directory " + dir1.absolute + " to " + dir2.absolute, res.err)
     }
   }
 
 
   object Make_Directory extends Scala.Fun_Strings("make_directory")
   {
     val here = Scala_Project.here
     def apply(args: List[String]): List[String] = apply_paths1(args, make_directory)
   }
 
   object Copy_Dir extends Scala.Fun_Strings("copy_dir")
   {
     val here = Scala_Project.here
     def apply(args: List[String]): List[String] = apply_paths2(args, copy_dir)
   }
 
 
   /* copy files */
 
   def copy_file(src: JFile, dst: JFile): Unit =
   {
     val target = if (dst.isDirectory) new JFile(dst, src.getName) else dst
     if (!File.eq(src, target)) {
       try {
         Files.copy(src.toPath, target.toPath,
           StandardCopyOption.COPY_ATTRIBUTES,
           StandardCopyOption.REPLACE_EXISTING)
       }
       catch {
         case ERROR(msg) =>
           cat_error("Failed to copy file " +
             File.path(src).absolute + " to " + File.path(dst).absolute, msg)
       }
     }
   }
 
   def copy_file(src: Path, dst: Path): Unit = copy_file(src.file, dst.file)
 
   def copy_file_base(base_dir: Path, src: Path, target_dir: Path): Unit =
   {
     val src1 = src.expand
     val src1_dir = src1.dir
     if (!src1.starts_basic) error("Illegal path specification " + src1 + " beyond base directory")
     copy_file(base_dir + src1, Isabelle_System.make_directory(target_dir + src1_dir))
   }
 
 
   object Copy_File extends Scala.Fun_Strings("copy_file")
   {
     val here = Scala_Project.here
     def apply(args: List[String]): List[String] = apply_paths2(args, copy_file)
   }
 
   object Copy_File_Base extends Scala.Fun_Strings("copy_file_base")
   {
     val here = Scala_Project.here
     def apply(args: List[String]): List[String] = apply_paths3(args, copy_file_base)
   }
 
 
   /* move files */
 
   def move_file(src: JFile, dst: JFile): Unit =
   {
     val target = if (dst.isDirectory) new JFile(dst, src.getName) else dst
     if (!File.eq(src, target))
       Files.move(src.toPath, target.toPath, StandardCopyOption.REPLACE_EXISTING)
   }
 
   def move_file(src: Path, dst: Path): Unit = move_file(src.file, dst.file)
 
 
   /* symbolic link */
 
   def symlink(src: Path, dst: Path, force: Boolean = false): Unit =
   {
     val src_file = src.file
     val dst_file = dst.file
     val target = if (dst_file.isDirectory) new JFile(dst_file, src_file.getName) else dst_file
 
     if (force) target.delete
 
+    def cygwin_link(): Unit =
+      Isabelle_Env.cygwin_link(File.standard_path(src), target)
+
     try { Files.createSymbolicLink(target.toPath, src_file.toPath) }
     catch {
-      case _: UnsupportedOperationException if Platform.is_windows =>
-        Cygwin.link(File.standard_path(src), target)
-      case _: FileSystemException if Platform.is_windows =>
-        Cygwin.link(File.standard_path(src), target)
+      case _: UnsupportedOperationException if Platform.is_windows => cygwin_link()
+      case _: FileSystemException if Platform.is_windows => cygwin_link()
     }
   }
 
 
   /* tmp files */
 
   def isabelle_tmp_prefix(): JFile =
   {
     val path = Path.explode("$ISABELLE_TMP_PREFIX")
     path.file.mkdirs  // low-level mkdirs to avoid recursion via Isabelle environment
     File.platform_file(path)
   }
 
   def tmp_file(name: String, ext: String = "", base_dir: JFile = isabelle_tmp_prefix()): JFile =
   {
     val suffix = if (ext == "") "" else "." + ext
     val file = Files.createTempFile(base_dir.toPath, name, suffix).toFile
     file.deleteOnExit
     file
   }
 
   def with_tmp_file[A](name: String, ext: String = "")(body: Path => A): A =
   {
     val file = tmp_file(name, ext)
     try { body(File.path(file)) } finally { file.delete }
   }
 
 
   /* tmp dirs */
 
   def rm_tree(root: JFile): Unit =
   {
     root.delete
     if (root.isDirectory) {
       Files.walkFileTree(root.toPath,
         new SimpleFileVisitor[JPath] {
           override def visitFile(file: JPath, attrs: BasicFileAttributes): FileVisitResult =
           {
             try { Files.deleteIfExists(file) }
             catch { case _: IOException => }
             FileVisitResult.CONTINUE
           }
 
           override def postVisitDirectory(dir: JPath, e: IOException): FileVisitResult =
           {
             if (e == null) {
               try { Files.deleteIfExists(dir) }
               catch { case _: IOException => }
               FileVisitResult.CONTINUE
             }
             else throw e
           }
         }
       )
     }
   }
 
   def rm_tree(root: Path): Unit = rm_tree(root.file)
 
   object Rm_Tree extends Scala.Fun_Strings("rm_tree")
   {
     val here = Scala_Project.here
     def apply(args: List[String]): List[String] = apply_paths1(args, rm_tree)
   }
 
   def tmp_dir(name: String, base_dir: JFile = isabelle_tmp_prefix()): JFile =
   {
     val dir = Files.createTempDirectory(base_dir.toPath, name).toFile
     dir.deleteOnExit
     dir
   }
 
   def with_tmp_dir[A](name: String)(body: Path => A): A =
   {
     val dir = tmp_dir(name)
     try { body(File.path(dir)) } finally { rm_tree(dir) }
   }
 
 
   /* quasi-atomic update of directory */
 
   def update_directory(dir: Path, f: Path => Unit): Unit =
   {
     val new_dir = dir.ext("new")
     val old_dir = dir.ext("old")
 
     rm_tree(new_dir)
     rm_tree(old_dir)
 
     f(new_dir)
 
     if (dir.is_dir) move_file(dir, old_dir)
     move_file(new_dir, dir)
     rm_tree(old_dir)
   }
 
 
 
   /** external processes **/
 
   /* GNU bash */
 
   def bash(script: String,
     cwd: JFile = null,
     env: Map[String, String] = settings(),
     redirect: Boolean = false,
     progress_stdout: String => Unit = (_: String) => (),
     progress_stderr: String => Unit = (_: String) => (),
     watchdog: Option[Bash.Watchdog] = None,
     strict: Boolean = true,
     cleanup: () => Unit = () => ()): Process_Result =
   {
     Bash.process(script, cwd = cwd, env = env, redirect = redirect, cleanup = cleanup).
       result(progress_stdout = progress_stdout, progress_stderr = progress_stderr,
         watchdog = watchdog, strict = strict)
   }
 
   private lazy val gnutar_check: Boolean =
     try { bash("tar --version").check.out.containsSlice("GNU tar") || error("") }
     catch { case ERROR(_) => false }
 
   def gnutar(
     args: String,
     dir: Path = Path.current,
     original_owner: Boolean = false,
     strip: Int = 0,
     redirect: Boolean = false): Process_Result =
   {
     val options =
       (if (dir.is_current) "" else "-C " + File.bash_path(dir) + " ") +
       (if (original_owner) "" else "--owner=root --group=staff ") +
       (if (strip <= 0) "" else "--strip-components=" + strip + " ")
 
     if (gnutar_check) bash("tar " + options + args, redirect = redirect)
     else error("Expected to find GNU tar executable")
   }
 
   def require_command(cmd: String, test: String = "--version"): Unit =
   {
     if (!bash(Bash.string(cmd) + " " + test).ok) error("Missing system command: " + quote(cmd))
   }
 
   def hostname(): String = bash("hostname -s").check.out
 
   def open(arg: String): Unit =
     bash("exec \"$ISABELLE_OPEN\" " + Bash.string(arg) + " >/dev/null 2>/dev/null &")
 
   def pdf_viewer(arg: Path): Unit =
     bash("exec \"$PDF_VIEWER\" " + File.bash_path(arg) + " >/dev/null 2>/dev/null &")
 
   def open_external_file(name: String): Boolean =
   {
     val ext = Library.take_suffix((c: Char) => c != '.', name.toList)._2.mkString
     val external =
       ext.nonEmpty &&
       Library.space_explode(':', getenv("ISABELLE_EXTERNAL_FILES")).contains(ext)
     if (external) {
       if (ext == "pdf" && Path.is_wellformed(name)) pdf_viewer(Path.explode(name))
       else open(name)
     }
     external
   }
 
   def export_isabelle_identifier(isabelle_identifier: String): String =
     if (isabelle_identifier == "") ""
     else "export ISABELLE_IDENTIFIER=" + Bash.string(isabelle_identifier) + "\n"
 
 
   /** Isabelle resources **/
 
   /* repository clone with Admin */
 
   def admin(): Boolean = Path.explode("~~/Admin").is_dir
 
 
   /* default logic */
 
   def default_logic(args: String*): String =
   {
     args.find(_ != "") match {
       case Some(logic) => logic
       case None => getenv_strict("ISABELLE_LOGIC")
     }
   }
 
 
   /* download file */
 
   def download(url_name: String, progress: Progress = new Progress): HTTP.Content =
   {
     val url = Url(url_name)
     progress.echo("Getting " + quote(url_name))
     try { HTTP.Client.get(url) }
     catch { case ERROR(msg) => cat_error("Failed to download " + quote(url_name), msg) }
   }
 
   def download_file(url_name: String, file: Path, progress: Progress = new Progress): Unit =
     Bytes.write(file, download(url_name, progress = progress).bytes)
 
   object Download extends Scala.Fun("download", thread = true)
   {
     val here = Scala_Project.here
     override def invoke(args: List[Bytes]): List[Bytes] =
       args match { case List(url) => List(download(url.text).bytes) }
   }
 
 
   /* repositories */
 
   val isabelle_repository: Mercurial.Server =
     Mercurial.Server("https://isabelle.sketis.net/repos/isabelle")
 
   val afp_repository: Mercurial.Server =
     Mercurial.Server("https://isabelle.sketis.net/repos/afp-devel")
 
   def official_releases(): List[String] =
     Library.trim_split_lines(
       isabelle_repository.read_file(Path.explode("Admin/Release/official")))
 }
diff --git a/src/Pure/build-jars b/src/Pure/build-jars
--- a/src/Pure/build-jars
+++ b/src/Pure/build-jars
@@ -1,330 +1,329 @@
 #!/usr/bin/env bash
 #
 # Author: Makarius
 #
 # build-jars - build Isabelle/Scala
 #
 # Requires proper Isabelle settings environment.
 
 ## sources
 
 declare -a SOURCES=(
   src/HOL/SPARK/Tools/spark.scala
   src/HOL/Tools/ATP/system_on_tptp.scala
   src/HOL/Tools/Mirabelle/mirabelle.scala
   src/HOL/Tools/Nitpick/kodkod.scala
   src/Pure/Admin/afp.scala
   src/Pure/Admin/build_csdp.scala
   src/Pure/Admin/build_cygwin.scala
   src/Pure/Admin/build_doc.scala
   src/Pure/Admin/build_e.scala
   src/Pure/Admin/build_fonts.scala
   src/Pure/Admin/build_history.scala
   src/Pure/Admin/build_jcef.scala
   src/Pure/Admin/build_jdk.scala
   src/Pure/Admin/build_jedit.scala
   src/Pure/Admin/build_log.scala
   src/Pure/Admin/build_polyml.scala
   src/Pure/Admin/build_release.scala
   src/Pure/Admin/build_spass.scala
   src/Pure/Admin/build_sqlite.scala
   src/Pure/Admin/build_status.scala
   src/Pure/Admin/build_vampire.scala
   src/Pure/Admin/build_verit.scala
   src/Pure/Admin/build_zipperposition.scala
   src/Pure/Admin/check_sources.scala
   src/Pure/Admin/ci_profile.scala
   src/Pure/Admin/isabelle_cronjob.scala
   src/Pure/Admin/isabelle_devel.scala
   src/Pure/Admin/jenkins.scala
   src/Pure/Admin/other_isabelle.scala
   src/Pure/Concurrent/consumer_thread.scala
   src/Pure/Concurrent/counter.scala
   src/Pure/Concurrent/delay.scala
   src/Pure/Concurrent/event_timer.scala
   src/Pure/Concurrent/future.scala
   src/Pure/Concurrent/isabelle_thread.scala
   src/Pure/Concurrent/mailbox.scala
   src/Pure/Concurrent/par_list.scala
   src/Pure/Concurrent/synchronized.scala
   src/Pure/GUI/color_value.scala
   src/Pure/GUI/desktop_app.scala
   src/Pure/GUI/gui.scala
   src/Pure/GUI/gui_thread.scala
   src/Pure/GUI/popup.scala
   src/Pure/GUI/wrap_panel.scala
   src/Pure/General/antiquote.scala
   src/Pure/General/bytes.scala
   src/Pure/General/cache.scala
   src/Pure/General/codepoint.scala
   src/Pure/General/comment.scala
   src/Pure/General/completion.scala
   src/Pure/General/csv.scala
   src/Pure/General/date.scala
   src/Pure/General/exn.scala
   src/Pure/General/file.scala
   src/Pure/General/file_watcher.scala
   src/Pure/General/graph.scala
   src/Pure/General/graph_display.scala
   src/Pure/General/graphics_file.scala
   src/Pure/General/http.scala
   src/Pure/General/json.scala
   src/Pure/General/linear_set.scala
   src/Pure/General/logger.scala
   src/Pure/General/long_name.scala
   src/Pure/General/mailman.scala
   src/Pure/General/mercurial.scala
   src/Pure/General/multi_map.scala
   src/Pure/General/output.scala
   src/Pure/General/path.scala
   src/Pure/General/position.scala
   src/Pure/General/pretty.scala
   src/Pure/General/properties.scala
   src/Pure/General/rdf.scala
   src/Pure/General/scan.scala
   src/Pure/General/sha1.scala
   src/Pure/General/sql.scala
   src/Pure/General/ssh.scala
   src/Pure/General/symbol.scala
   src/Pure/General/time.scala
   src/Pure/General/timing.scala
   src/Pure/General/untyped.scala
   src/Pure/General/url.scala
   src/Pure/General/utf8.scala
   src/Pure/General/uuid.scala
   src/Pure/General/value.scala
   src/Pure/General/word.scala
   src/Pure/General/xz.scala
   src/Pure/Isar/document_structure.scala
   src/Pure/Isar/keyword.scala
   src/Pure/Isar/line_structure.scala
   src/Pure/Isar/outer_syntax.scala
   src/Pure/Isar/parse.scala
   src/Pure/Isar/token.scala
   src/Pure/ML/ml_console.scala
   src/Pure/ML/ml_lex.scala
   src/Pure/ML/ml_process.scala
   src/Pure/ML/ml_profiling.scala
   src/Pure/ML/ml_statistics.scala
   src/Pure/ML/ml_syntax.scala
   src/Pure/PIDE/byte_message.scala
   src/Pure/PIDE/command.scala
   src/Pure/PIDE/command_span.scala
   src/Pure/PIDE/document.scala
   src/Pure/PIDE/document_id.scala
   src/Pure/PIDE/document_status.scala
   src/Pure/PIDE/editor.scala
   src/Pure/PIDE/headless.scala
   src/Pure/PIDE/line.scala
   src/Pure/PIDE/markup.scala
   src/Pure/PIDE/markup_tree.scala
   src/Pure/PIDE/protocol.scala
   src/Pure/PIDE/protocol_handlers.scala
   src/Pure/PIDE/protocol_message.scala
   src/Pure/PIDE/prover.scala
   src/Pure/PIDE/query_operation.scala
   src/Pure/PIDE/rendering.scala
   src/Pure/PIDE/resources.scala
   src/Pure/PIDE/session.scala
   src/Pure/PIDE/text.scala
   src/Pure/PIDE/xml.scala
   src/Pure/PIDE/yxml.scala
   src/Pure/ROOT.scala
   src/Pure/System/bash.scala
   src/Pure/System/command_line.scala
   src/Pure/System/components.scala
-  src/Pure/System/cygwin.scala
   src/Pure/System/executable.scala
   src/Pure/System/getopts.scala
   src/Pure/System/isabelle_charset.scala
   src/Pure/System/isabelle_env.scala
   src/Pure/System/isabelle_fonts.scala
   src/Pure/System/isabelle_platform.scala
   src/Pure/System/isabelle_process.scala
   src/Pure/System/isabelle_system.scala
   src/Pure/System/isabelle_tool.scala
   src/Pure/System/java_statistics.scala
   src/Pure/System/linux.scala
   src/Pure/System/mingw.scala
   src/Pure/System/numa.scala
   src/Pure/System/options.scala
   src/Pure/System/platform.scala
   src/Pure/System/posix_interrupt.scala
   src/Pure/System/process_result.scala
   src/Pure/System/progress.scala
   src/Pure/System/scala.scala
   src/Pure/System/system_channel.scala
   src/Pure/System/tty_loop.scala
   src/Pure/Thy/bibtex.scala
   src/Pure/Thy/document_build.scala
   src/Pure/Thy/export.scala
   src/Pure/Thy/export_theory.scala
   src/Pure/Thy/file_format.scala
   src/Pure/Thy/html.scala
   src/Pure/Thy/latex.scala
   src/Pure/Thy/presentation.scala
   src/Pure/Thy/sessions.scala
   src/Pure/Thy/thy_element.scala
   src/Pure/Thy/thy_header.scala
   src/Pure/Thy/thy_syntax.scala
   src/Pure/Tools/build.scala
   src/Pure/Tools/build_docker.scala
   src/Pure/Tools/build_job.scala
   src/Pure/Tools/check_keywords.scala
   src/Pure/Tools/debugger.scala
   src/Pure/Tools/doc.scala
   src/Pure/Tools/dump.scala
   src/Pure/Tools/fontforge.scala
   src/Pure/Tools/java_monitor.scala
   src/Pure/Tools/logo.scala
   src/Pure/Tools/main.scala
   src/Pure/Tools/mkroot.scala
   src/Pure/Tools/phabricator.scala
   src/Pure/Tools/print_operation.scala
   src/Pure/Tools/profiling_report.scala
   src/Pure/Tools/scala_project.scala
   src/Pure/Tools/server.scala
   src/Pure/Tools/server_commands.scala
   src/Pure/Tools/simplifier_trace.scala
   src/Pure/Tools/spell_checker.scala
   src/Pure/Tools/task_statistics.scala
   src/Pure/Tools/update.scala
   src/Pure/Tools/update_cartouches.scala
   src/Pure/Tools/update_comments.scala
   src/Pure/Tools/update_header.scala
   src/Pure/Tools/update_then.scala
   src/Pure/Tools/update_theorems.scala
   src/Pure/library.scala
   src/Pure/pure_thy.scala
   src/Pure/term.scala
   src/Pure/term_xml.scala
   src/Pure/thm_name.scala
   src/Tools/Graphview/graph_file.scala
   src/Tools/Graphview/graph_panel.scala
   src/Tools/Graphview/graphview.scala
   src/Tools/Graphview/layout.scala
   src/Tools/Graphview/main_panel.scala
   src/Tools/Graphview/metrics.scala
   src/Tools/Graphview/model.scala
   src/Tools/Graphview/mutator.scala
   src/Tools/Graphview/mutator_dialog.scala
   src/Tools/Graphview/mutator_event.scala
   src/Tools/Graphview/popups.scala
   src/Tools/Graphview/shapes.scala
   src/Tools/Graphview/tree_panel.scala
   src/Tools/VSCode/src/build_vscode.scala
   src/Tools/VSCode/src/channel.scala
   src/Tools/VSCode/src/dynamic_output.scala
   src/Tools/VSCode/src/language_server.scala
   src/Tools/VSCode/src/lsp.scala
   src/Tools/VSCode/src/preview_panel.scala
   src/Tools/VSCode/src/state_panel.scala
   src/Tools/VSCode/src/textmate_grammar.scala
   src/Tools/VSCode/src/vscode_model.scala
   src/Tools/VSCode/src/vscode_rendering.scala
   src/Tools/VSCode/src/vscode_resources.scala
   src/Tools/VSCode/src/vscode_spell_checker.scala
 )
 
 
 ## diagnostics
 
 PRG="$(basename "$0")"
 
 function usage()
 {
   echo
   echo "Usage: isabelle $PRG [OPTIONS]"
   echo
   echo "  Options are:"
   echo "    -f           fresh build"
   echo
   exit 1
 }
 
 function fail()
 {
   echo "$1" >&2
   exit 2
 }
 
 [ -z "$ISABELLE_HOME" ] && fail "Missing Isabelle settings environment"
 
 
 ## process command line
 
 # options
 
 FRESH=""
 
 while getopts "f" OPT
 do
   case "$OPT" in
     f)
       FRESH=true
       ;;
     \?)
       usage
       ;;
   esac
 done
 
 shift $(($OPTIND - 1))
 
 
 # args
 
 [ "$#" -ne 0 ] && usage
 
 
 ## target
 
 TARGET_DIR="lib/classes"
 TARGET_JAR="$TARGET_DIR/Pure.jar"
 TARGET_SHASUM="$TARGET_DIR/Pure.shasum"
 
 function target_shasum()
 {
   shasum -a1 -b "$TARGET_JAR" "${SOURCES[@]}" 2>/dev/null
 }
 
 function target_clean()
 {
   rm -rf "$TARGET_DIR"
 }
 
 [ -n "$FRESH" ] && target_clean
 
 
 ## build
 
 target_shasum | cmp "$TARGET_SHASUM" >/dev/null 2>/dev/null
 if [ "$?" -ne 0 ]; then
   echo "### Building Isabelle/Scala ..."
 
   target_clean
 
   BUILD_DIR="$TARGET_DIR/build"
   mkdir -p "$BUILD_DIR"
 
   (
     export CLASSPATH="$(platform_path "$ISABELLE_CLASSPATH")"
     isabelle_scala scalac $ISABELLE_SCALAC_OPTIONS \
       -d "$BUILD_DIR" "${SOURCES[@]}"
   ) || fail "Failed to compile sources"
 
   CHARSET_SERVICE="META-INF/services/java.nio.charset.spi.CharsetProvider"
   mkdir -p "$BUILD_DIR/$(dirname "$CHARSET_SERVICE")"
   echo isabelle.Isabelle_Charset_Provider > "$BUILD_DIR/$CHARSET_SERVICE"
 
   cp "$ISABELLE_HOME/lib/logo/isabelle_transparent-32.gif" "$BUILD_DIR/isabelle/."
   cp "$ISABELLE_HOME/lib/logo/isabelle_transparent.gif" "$BUILD_DIR/isabelle/."
 
   isabelle_jdk jar -c -f "$(platform_path "$TARGET_JAR")" -e isabelle.Main \
     -C "$BUILD_DIR" META-INF \
     -C "$BUILD_DIR" isabelle || fail "Failed to produce $TARGET_JAR"
 
   rm -rf "$BUILD_DIR"
 
   target_shasum > "$TARGET_SHASUM"
 fi