When requesting files, send the etag in an If-None-Match HTTP header, rather than calling HEAD and then GET.
When requesting files, send the etag in an If-None-Match HTTP header, rather than calling HEAD and then GET.

This lets us issue a single request per file. Note that this assumes the server uses the MD5 of a file's content as its etag, which is true for Amazon S3. Proper HTTP compliance would be to save the server's etag from the response HTTP headers

ludomade/grunt-shampoo