Add spack purge --cache to purge local archive cache.

.gitignore

@@ -1,4 +1,5 @@
 /var/spack/stage
+/var/spack/cache
 *.pyc
 /opt/
 *~

lib/spack/spack/cmd/purge.py

@@ -22,9 +22,31 @@
 # License along with this program; if not, write to the Free Software
 # Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 ##############################################################################
+import spack
 import spack.stage as stage
 
-description = "Remove all temporary build files and downloaded archives"
+description = "Remove temporary build files and/or downloaded archives"
+
+
+def setup_parser(subparser):
+    subparser.add_argument(
+        '-s', '--stage', action='store_true', default=True,
+        help="Remove all temporary build stages (default).")
+    subparser.add_argument(
+        '-c', '--cache', action='store_true', help="Remove cached downloads.")
+    subparser.add_argument(
+        '-a', '--all', action='store_true',
+        help="Remove all of the above.")
+
 
 def purge(parser, args):
+    # Special case: no flags.
+    if not any((args.stage, args.cache, args.all)):
         stage.purge()
+        return
+
+    # handle other flags with fall through.
+    if args.stage or args.all:
+        stage.purge()
+    if args.cache or args.all:
+        spack.cache.destroy()

lib/spack/spack/fetch_strategy.py

@@ -858,6 +858,9 @@ def fetcher(self, targetPath, digest):
         url = "file://" + join_path(self.root, targetPath)
         return CacheURLFetchStrategy(url, digest)
 
+    def destroy(self):
+        shutil.rmtree(self.root, ignore_errors=True)
+
 
 class FetchError(spack.error.SpackError):