resources : added docs fixes #1551 (#1627)

lib/spack/docs/packaging_guide.rst

@@ -759,6 +759,26 @@ Fetching a revision
 Subversion branches are handled as part of the directory structure, so
 you can check out a branch or tag by changing the ``url``.
 
+Expanding additional resources in the source tree
+-------------------------------------------------
+
+Some packages (most notably compilers) provide optional features if additional
+resources are expanded within their source tree before building. In Spack it is
+possible to describe such a need with the ``resource`` directive :
+
+  .. code-block:: python
+
+     resource(
+        name='cargo',
+        git='https://github.com/rust-lang/cargo.git',
+        tag='0.10.0',
+        destination='cargo'
+     )
+
+Based on the keywords present among the arguments the appropriate ``FetchStrategy``
+will be used for the resource. The keyword ``destination`` is relative to the source
+root of the package and should point to where the resource is to be expanded.
+
 Automatic caching of files fetched during installation
 ------------------------------------------------------
 

lib/spack/spack/directives.py

@@ -292,17 +292,17 @@ def resource(pkg, **kwargs):
     Define an external resource to be fetched and staged when building the
     package. Based on the keywords present in the dictionary the appropriate
     FetchStrategy will be used for the resource. Resources are fetched and
-    staged in their own folder inside spack stage area, and then linked into
+    staged in their own folder inside spack stage area, and then moved into
     the stage area of the package that needs them.
 
     List of recognized keywords:
 
     * 'when' : (optional) represents the condition upon which the resource is
     needed
-    * 'destination' : (optional) path where to link the resource. This path
+    * 'destination' : (optional) path where to move the resource. This path
     must be relative to the main package stage area.
     * 'placement' : (optional) gives the possibility to fine tune how the
-    resource is linked into the main package stage area.
+    resource is moved into the main package stage area.
     """
     when = kwargs.get('when', pkg.name)
     destination = kwargs.get('destination', "")