Merge pull request #80 from heroku/only-prune-on-cache-restore

only prune when node_modules directory is restored from cache. Fixes #75

bin/compile

@@ -62,15 +62,15 @@ if test -d $build_dir/node_modules; then
 elif test -d $cache_dir/node_modules; then
   status "Restoring node_modules directory from cache"
   cp -r $cache_dir/node_modules $build_dir/
+
+  status "Pruning cached dependencies not specified in package.json"
+  npm prune 2>&1 | indent
 fi
 
 # Make npm output to STDOUT instead of its default STDERR
 status "Installing dependencies"
 npm install --userconfig $build_dir/.npmrc --production 2>&1 | indent
 
-status "Pruning dependencies not specified in package.json"
-npm prune 2>&1 | indent
-
 status "Caching node_modules directory for future builds"
 rm -rf $cache_dir
 mkdir -p $cache_dir