[Rirusha]

Use an existing reverse-DNS ID from os-release when it prefixed with the

rdns of HOME_URL or passes the known-TLD check.

closes #801

[ximion]

The tests also look fairly verbose to me, I think it would be nicer to simply test the positive case ("ID is already rDNS") and the negative case ("ID isn't rDNS"), because the other things like invalid IDs are already tested in other parts of the testsuite.

This can also be compacted a lot by just having the test generate the os-release file into a temporary location, then you could just change the values in a loop and make a more compact test with no extra files.

[ximion]

This looks quite redundant - the logic should be "if the ID already looks like rDNS, we simply copy it over as cid and stop guessing from the homepage". So, something like this would be what I would have in mind here:

/* the OS ID may already be an rDNS ID (e.g. org.freedesktop.platform), don't prefix it again */
          if (priv->os_id != NULL) {
                  g_auto(GStrv) id_parts = g_strsplit (priv->os_id, ".", 3);
                  if (g_strv_length (id_parts) == 3 && as_utils_is_tld (id_parts[0])) {
                          priv->os_cid = g_strdup (priv->os_id);
                          return priv->os_cid;
                  }
          }

That way, you can drop the other code and no redundant calls to as_utils_dns_to_rdns happen, that should make this code really small.