src/Pure/System/isabelle_system.scala

--- a/src/Pure/System/isabelle_system.scala	Wed Apr 28 23:20:05 2021 +0200
+++ b/src/Pure/System/isabelle_system.scala	Thu Apr 29 15:49:04 2021 +0200
@@ -626,4 +626,8 @@
 
   val afp_repository: Mercurial.Address =
     Mercurial.Address("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")))
 }