clarified signature;

--- a/src/Pure/Admin/build_release.scala	Mon Dec 03 20:04:48 2018 +0100
+++ b/src/Pure/Admin/build_release.scala	Mon Dec 03 20:34:19 2018 +0100
@@ -328,7 +328,9 @@
           progress = progress)
 
       other_isabelle.init_settings(
-        other_isabelle.init_components(base = Components.contrib(base_dir.absolute)))
+        other_isabelle.init_components(
+          base = Components.contrib(base_dir.absolute),
+          catalogs = List("main")))
       other_isabelle.resolve_components(echo = true)
 
       try {

--- a/src/Pure/Admin/other_isabelle.scala	Mon Dec 03 20:04:48 2018 +0100
+++ b/src/Pure/Admin/other_isabelle.scala	Mon Dec 03 20:34:19 2018 +0100
@@ -69,16 +69,17 @@
   /* components */
 
   def default_components_base: Path = Components.contrib(isabelle_home_user.absolute.dir)
-  def default_components_dir: Path = Components.admin(isabelle_home.absolute)
-  def default_catalogs: List[String] = List("main")
 
   def init_components(
     base: Path = default_components_base,
-    dir: Path = default_components_dir,
-    catalogs: List[String] = default_catalogs): List[String] =
+    catalogs: List[String] = Nil,
+    components: List[String] = Nil): List[String] =
   {
-    catalogs.map(catalog =>
-      "init_components " + File.bash_path(base) + " " + File.bash_path(dir + Path.basic(catalog)))
+    val dir = Components.admin(isabelle_home.absolute)
+    catalogs.map(name =>
+      "init_components " + File.bash_path(base) + " " + File.bash_path(dir + Path.basic(name))) :::
+    components.map(name =>
+      "init_component " + File.bash_path(base + Path.basic(name)))
   }