support git remotes that need http basic auth

using git credential to get the password

One thing this doesn't do is wrap the password prompting inside the prompt
action. So with -J, the output can be a bit garbled.

Remote/Web.hs

@@ -90,7 +90,7 @@ downloadKey key _af dest p = unVerified $ get =<< getWebUrls key
 			YoutubeDownloader -> do
 				showOutput
 				youtubeDlTo key u' dest
-			_ -> downloadUrl key p [u'] dest
+			_ -> Url.withUrlOptions $ downloadUrl key p [u'] dest
 
 downloadKeyCheap :: Key -> AssociatedFile -> FilePath -> Annex Bool
 downloadKeyCheap _ _ _ = return False