tools.deploy.backend: add word for deleting cached staging images.

basis/tools/deploy/backend/backend.factor

@@ -65,6 +65,13 @@ ERROR: can't-deploy-library-file library ;
     "-" join "." my-arch 3append
     "staging." ".image" surround cache-file ;
 
+: delete-staging-images ( -- )
+    cache-directory [
+        [ "staging." head? ] filter
+        "." my-arch ".image" 3append [ tail? ] curry filter
+        [ delete-file ] each
+    ] with-directory-files ;
+
 : staging-command-line ( profile -- flags )
     [
         [

basis/tools/deploy/deploy-tests.factor

@@ -10,11 +10,7 @@ IN: tools.deploy.tests
 ! Delete all cached staging images in case syntax or
 ! other core vocabularies have changed and staging
 ! images are stale.
-cache-directory [
-    [ "staging." head? ] filter
-    my-arch ".image" append [ tail? ] curry filter
-    [ delete-file ] each
-] with-directory-files
+delete-staging-images
 
 [ "nosuchvocab" deploy ] [ no-vocab? ] must-fail-with