Use http-conduit for url downloads by default, annex.web-options enables curl

* For url downloads, git-annex now defaults to using a http library,
  rather than wget or curl. But, if annex.web-options is set, it will
  use curl. To use the .netrc file, run:
    git config annex.web-options --netrc
* git-annex no longer uses wget (and wget is no longer shipped with
  git-annex builds).

Note that curl is always run in silent mode, since the new API for
download has a MeterUpdate and doesn't make way for curl progress
output. It might be worth writing a parser for curl's progress output
to update the meter when using it, but I didn't bother with this edge
case for now.

This commit was supported by the NSF-funded DataLad project.

Assistant/Upgrade.hs

@@ -36,6 +36,7 @@ import Utility.Tmp.Dir
 import Utility.UserInfo
 import Utility.Gpg
 import Utility.FileMode
+import Utility.Metered
 import qualified Utility.Lsof as Lsof
 import qualified BuildInfo
 import qualified Utility.Url as Url
@@ -322,8 +323,8 @@ downloadDistributionInfo = do
 	liftIO $ withTmpDir "git-annex.tmp" $ \tmpdir -> do
 		let infof = tmpdir </> "info"
 		let sigf = infof ++ ".sig"
-		ifM (Url.downloadQuiet distributionInfoUrl infof uo
-			<&&> Url.downloadQuiet distributionInfoSigUrl sigf uo
+		ifM (Url.download nullMeterUpdate distributionInfoUrl infof uo
+			<&&> Url.download nullMeterUpdate distributionInfoSigUrl sigf uo
 			<&&> verifyDistributionSig gpgcmd sigf)
 			( parseInfoFile <$> readFileStrict infof
 			, return Nothing