proper ISABELLE_IDENTIFIER for remote Admin/build_history, e.g. relevant for settings;

--- a/src/Pure/Admin/build_history.scala	Wed May 24 11:39:00 2017 +0200
+++ b/src/Pure/Admin/build_history.scala	Wed May 24 15:04:13 2017 +0200
@@ -403,6 +403,7 @@
     isabelle_repos_self: Path,
     isabelle_repos_other: Path,
     isabelle_repos_source: String = "http://isabelle.in.tum.de/repos/isabelle",
+    isabelle_identifier: String = default_isabelle_identifier,
     self_update: Boolean = false,
     push_isabelle_home: Boolean = false,
     progress: Progress = No_Progress,
@@ -454,6 +455,7 @@
 
       val process_result =
         ssh.execute(
+          Isabelle_System.export_isabelle_identifier(isabelle_identifier) +
           ssh.bash_path(isabelle_admin + Path.explode("build_history")) +
             " -o " + ssh.bash_path(output_file) + " " + options + " " +
             ssh.bash_path(isabelle_repos_other) + " " + args,

--- a/src/Pure/Admin/isabelle_cronjob.scala	Wed May 24 11:39:00 2017 +0200
+++ b/src/Pure/Admin/isabelle_cronjob.scala	Wed May 24 15:04:13 2017 +0200
@@ -235,6 +235,7 @@
                   isabelle_repos,
                   isabelle_repos.ext(r.host),
                   isabelle_repos_source = isabelle_dev_source,
+                  isabelle_identifier = "cronjob_build_history",
                   self_update = self_update,
                   push_isabelle_home = push_isabelle_home,
                   options =