Recover the complicated situation after my bad merge

I made a mistake merge.  Reverting it in c778945806 undid the state
on master, but now I realize it crippled the git merge mechanism.
As the merge contained a mix of commits from `master..staging-next`
and other commits from `staging-next..staging`, it got the
`staging-next` branch into a state that was difficult to recover.

I reconstructed the "desired" state of staging-next tree by:
 - checking out the last commit of the problematic range: 4effe769e2
 - `git rebase -i --preserve-merges a8a018ddc0` - dropping the mistaken
   merge commit and its revert from that range (while keeping
   reapplication from 4effe769e2)
 - merging the last unaffected staging-next commit (803ca85c20)
 - fortunately no other commits have been pushed to staging-next yet
 - applying a diff on staging-next to get it into that state

pkgs/development/libraries/libwebp/default.nix

@@ -1,4 +1,4 @@
-{ stdenv, fetchurl
+{ stdenv, fetchFromGitHub, autoreconfHook, libtool
 , threadingSupport ? true # multi-threading
 , openglSupport ? false, freeglut ? null, libGL ? null, libGLU ? null # OpenGL (required for vwebp)
 , pngSupport ? true, libpng ? null # PNG image format
@@ -27,13 +27,17 @@ in
 with stdenv.lib;
 stdenv.mkDerivation rec {
   pname = "libwebp";
-  version = "1.0.3";
+  version = "1.1.0";
 
-  src = fetchurl {
-    url = "http://downloads.webmproject.org/releases/webp/${pname}-${version}.tar.gz";
-    sha256 = "0kxk4sic34bln3k09mml7crvrmhj97swdk7b1ahbp5w6bj30f2p2";
+  src = fetchFromGitHub {
+    owner  = "webmproject";
+    repo   = pname;
+    rev    = version;
+    sha256 = "1kl6qqa29ygqb2fpv140y59v539gdqx4vcf3mlaxhca2bks98qgm";
   };
 
+  prePatch = "patchShebangs .";
+
   configureFlags = [
     (mkFlag threadingSupport "threading")
     (mkFlag openglSupport "gl")
@@ -50,6 +54,7 @@ stdenv.mkDerivation rec {
     (mkFlag libwebpdecoderSupport "libwebpdecoder")
   ];
 
+  nativeBuildInputs = [ autoreconfHook libtool ];
   buildInputs = [ ]
     ++ optionals openglSupport [ freeglut libGL libGLU ]
     ++ optional pngSupport libpng