make curl show http errors to stderr

* Run curl with -S, so HTTP errors are displayed, even when
  it's otherwise silent.
* When downloading in --json or --quiet mode, use curl in preference
  to wget, since curl is able to display only errors to stderr, unlike
  wget.

This does mean that downloadQuiet is only silent on stdout, not necessarily
on stderr, which affects a couple other calls of it. For example,
downloading the .git/config of a http remote may show an error message now,
perhaps with slightly suboptimal formatting due to other output.

1 files changed, 14 insertions, 8 deletions

diff --git a/Utility/Url.hs b/Utility/Url.hs
index 166783e09..1b68dce7f 100644
--- a/Utility/Url.hs
+++ b/Utility/Url.hs
@@ -246,17 +246,16 @@ headRequest r = r
 		(requestHeaders r)
 	}
 
-{- Used to download large files, such as the contents of keys.
+{- Download a perhaps large file, with auto-resume of incomplete downloads.
  -
- - Uses wget or curl program for its progress bar. (Wget has a better one,
- - so is preferred.) Which program to use is determined at run time; it
- - would not be appropriate to test at configure time and build support
- - for only one in.
+ - Uses wget or curl program for its progress bar and resuming support. 
+ - Which program to use is determined at run time depending on which is
+ - in path and which works best in a particular situation.
  -}
 download :: URLString -> FilePath -> UrlOptions -> IO Bool
 download = download' False
 
-{- No output, even on error. -}
+{- No output to stdout. -}
 downloadQuiet :: URLString -> FilePath -> UrlOptions -> IO Bool
 downloadQuiet = download' True
 
@@ -265,6 +264,12 @@ download' quiet url file uo = do
 	case parseURIRelaxed url of
 		Just u
 			| uriScheme u == "file:" -> curl
+			-- curl is preferred in quiet mode, because
+			-- it displays http errors to stderr, while wget
+			-- does not display them in quiet mode
+			| quiet -> ifM (inPath "curl") (curl, wget)
+			-- wget is preferred mostly because it has a better
+			-- progress bar
 			| otherwise -> ifM (inPath "wget") (wget , curl)
 		_ -> return False
   where
@@ -275,7 +280,8 @@ download' quiet url file uo = do
 	 - support, or need that option.
 	 -
 	 - When the wget version is new enough, pass options for
-	 - a less cluttered download display.
+	 - a less cluttered download display. Using -nv rather than -q
+	 - avoids most clutter while still displaying http errors.
 	 -}
 #ifndef __ANDROID__
 	wgetparams = concat
@@ -296,7 +302,7 @@ download' quiet url file uo = do
 		-- curl does not create destination file
 		-- if the url happens to be empty, so pre-create.
 		writeFile file ""
-		go "curl" $ headerparams ++ quietopt "-s" ++
+		go "curl" $ headerparams ++ quietopt "-sS" ++
 			[ Param "-f"
 			, Param "-L"
 			, Param "-C", Param "-"