New folder guard to stay in current folder

src/alire-os_lib.adb

@@ -62,6 +62,18 @@ package body Alire.OS_Lib is
       end return;
    end Enter_Folder;
 
+   ----------------------------
+   -- Stay_In_Current_Folder --
+   ----------------------------
+
+   function Stay_In_Current_Folder return Folder_Guard is
+   begin
+      return Guard : Folder_Guard (0) do
+         Log ("Staying in current folder", Debug);
+         Guard.Initialized := False;
+      end return;
+   end Stay_In_Current_Folder;
+
    --------------
    -- Finalize --
    --------------

src/alire-os_lib.ads

@@ -15,7 +15,9 @@ package Alire.OS_Lib is
    --  use this type in conjunction with Enter_Folder to ensure that 
    --  the CWD is modified and restored when creating/destroying the Folder_Guard
    
-   function Enter_Folder (Path : String) return Folder_Guard;
+   function Enter_Folder (Path : String) return Folder_Guard; 
+   
+   function Stay_In_Current_Folder return Folder_Guard;
    
    function "/" (L, R : String) return String is
      (Ada.Directories.Compose (L, R));
@@ -23,7 +25,7 @@ package Alire.OS_Lib is
    
 private
    
-   type Folder_Guard (Original_Len : Positive) is new Ada.Finalization.Limited_Controlled with record
+   type Folder_Guard (Original_Len : Natural) is new Ada.Finalization.Limited_Controlled with record
       Original    : String (1 .. Original_Len);
       Initialized : Boolean := False;
    end record;