diff -r d67d28254ff2 -r e378e0468ef2 src/Pure/General/mercurial.scala
--- a/src/Pure/General/mercurial.scala	Sat Oct 21 18:19:11 2017 +0200
+++ b/src/Pure/General/mercurial.scala	Sun Oct 22 13:12:38 2017 +0200
@@ -16,6 +16,9 @@
 
 object Mercurial
 {
+  type Graph = isabelle.Graph[String, Unit]
+
+
   /* command-line syntax */
 
   def optional(s: String, prefix: String = ""): String =
@@ -119,7 +122,7 @@
     def known_files(): List[String] =
       hg.command("status", options = "--modified --added --clean --no-status").check.out_lines
 
-    def graph(): Graph[String, Unit] =
+    def graph(): Graph =
     {
       val Node = """^node: (\w{12}) (\w{12}) (\w{12})""".r
       val log_result =