Only download the zip files if necessary

[marcelometal]

Using HTTP headers we can avoid to download the same file.

Headers: Last-Modified and Content-Length

$ curl -I http://agencia.tse.jus.br/estatistica/sead/odsele/consulta_cand/consulta_cand_2018.zip

HTTP/1.1 200 OK
Server: Apache/2.2.15 (Red Hat)
Last-Modified: Mon, 16 Nov 2020 01:00:05 GMT
ETag: "10118c-641f67-5b42ee6194614"
Accept-Ranges: bytes
Content-Length: 6561639
Content-Type: application/zip
F5-IpCliente: 189.36.X.X
ClientIP: 189.36.X.X
Server: thttpd/2.26 ??apr2004
Date: Mon, 16 Nov 2020 03:05:31 GMT
Connection: keep-alive
Set-Cookie: BIGipServerPool_Apache=197961920.20480.0000; path=/; Httponly