Generate unique subdirs for built elements

Based on issue 89 (https://gitlab.com/BuildStream/buildstream/issues/89)
Ensuring that elements are staged into unique subdirs while building.
This patch supports that by doing the following:

* Modify project config to add 2 new variables ("project-name" and "element-name")
* Changed the default install-root from "/buildstream/install" to "/buildstream-install"
* Update the tests to accommodate these changes
* Update the expected cache keys in the tests

This fixes #89

4 files changed, 9 insertions, 12 deletions

diff --git a/buildstream/buildelement.py b/buildstream/buildelement.py
index c275cfb9d..5a986bd11 100644
--- a/buildstream/buildelement.py
+++ b/buildstream/buildelement.py
@@ -90,7 +90,7 @@ of the staged sources.
 Result collection
 ~~~~~~~~~~~~~~~~~
 Finally, the resulting build *artifact* is collected from the the ``%{install-root}``
-directory (which is normally configured as ``/buildstream/install``) inside the sandbox.
+directory (which is normally configured as ``/buildstream-install``) inside the sandbox.
 
 All build elements must install into the ``%{install-root}`` using whatever
 semantic the given build system provides to do this. E.g. for standard autotools
@@ -222,7 +222,7 @@ class BuildElement(Element):
                       "will not be allowed to stage to %{build-root}.")
 
         # Return the payload, this is configurable but is generally
-        # always the /buildstream/install directory
+        # always the /buildstream-install directory
         return self.get_variable('install-root')
 
     def _get_commands(self, node, name):
diff --git a/buildstream/data/projectconfig.yaml b/buildstream/data/projectconfig.yaml
index 408304544..b4ad2dcb9 100644
--- a/buildstream/data/projectconfig.yaml
+++ b/buildstream/data/projectconfig.yaml
@@ -29,6 +29,10 @@ variables:
   # Note: this value defaults to the number of cores available
   max-jobs: 4
 
+  # Note: These variables are defined later on in element.py and _project.py
+  element-name: ""
+  project-name: ""
+
   # Path configuration, to be used in build instructions.
   #
   prefix: "/usr"
@@ -50,10 +54,10 @@ variables:
 
   # Indicates the default build directory where input is
   # normally staged
-  build-root: /buildstream/build
+  build-root: /buildstream/%{project-name}/%{element-name}
 
   # Indicates the build installation directory in the sandbox
-  install-root: /buildstream/install
+  install-root: /buildstream-install
 
   # Arguments for tooling used when stripping debug symbols
   objcopy-link-args: --add-gnu-debuglink
diff --git a/buildstream/element.py b/buildstream/element.py
index 8532f995c..131a834e1 100644
--- a/buildstream/element.py
+++ b/buildstream/element.py
@@ -173,6 +173,7 @@ class Element(Plugin):
 
         # Collect the composited variables and resolve them
         variables = self.__extract_variables(meta)
+        variables['element-name'] = self.name
         self.__variables = Variables(variables)
 
         # Collect the composited environment now that we have variables
diff --git a/buildstream/plugins/elements/script.yaml b/buildstream/plugins/elements/script.yaml
index 56a656cf6..b388378da 100644
--- a/buildstream/plugins/elements/script.yaml
+++ b/buildstream/plugins/elements/script.yaml
@@ -1,15 +1,7 @@
 # Common script element variables
 variables:
-  # Defines the directory that output is collected from once commands
-  # have been run.
-  install-root: /buildstream/install
-  #
   # Defines the directory commands will be run from.
   cwd: /
-  #
-  # Not directly used, but expected to be used when staging elements to be
-  # worked on.
-  build-root: /buildstream/build
 
 # Script element configuration
 config: