Create Instance from single Release

src/alire-containers.adb

@@ -0,0 +1,14 @@
+package body Alire.Containers is
+
+   ------------
+   -- To_Map --
+   ------------
+
+   function To_Map (R : Releases.Release) return Release_Map is
+   begin
+      return M : Release_Map do
+         M.Include (R.Project, R);
+      end return;
+   end To_Map;
+
+end Alire.Containers;

src/alire-containers.ads

@@ -24,5 +24,7 @@ package Alire.Containers with Preelaborate is
    package Project_Release_Maps is new Ada.Containers.Indefinite_Ordered_Maps
      (Project_Name, Releases.Release, "<", Releases."=");
    subtype Release_Map is Project_Release_Maps.Map;
+   
+   function To_Map (R : Releases.Release) return Release_Map;
 
 end Alire.Containers;

src/alire-index.ads

@@ -16,6 +16,8 @@ package Alire.Index is
    
    subtype Solution     is Containers.Version_Map; -- A dependence-valid mapping of project -> version
    subtype Instance     is Containers.Release_Map; -- A list of releases complying with a Solution
+   
+   Empty_Instance : constant Instance := Containers.Project_Release_Maps.Empty_Map;
       
    function V (Semantic_Version : String) return Semantic_Versioning.Version 
                renames Semantic_Versioning.New_Version;

src/alire-repositories-local.ads

@@ -7,6 +7,8 @@ package Alire.Repositories.Local is
    
    Repo : constant Repository;  
    
+   Local_Id : constant Release_Id;
+   
    overriding function Image (Repo : Repository) return String is 
      (raise Program_Error);
    
@@ -18,5 +20,7 @@ private
    type Repository is new Repositories.Repository with null record;
       
    Repo : constant Repository := (Repositories.Repository with null record); 
+   
+   Local_Id : constant Release_Id := "local"; -- not "" because that fails assertion on length
 
 end Alire.Repositories.Local;