picard: Patch in path of AcoustED fingerprinter.

That way we have the fingerprinter preselected in the configuration file
and the user doesn't need to search with an "open file" dialog inside
the Nix store.

Signed-off-by: aszlig <aszlig@redmoonstudios.org>

pkgs/applications/audio/picard/default.nix

@@ -1,5 +1,6 @@
 { stdenv, fetchurl, pythonPackages, gettext, pyqt4
-, pkgconfig, libdiscid, libofa, ffmpeg }:
+, pkgconfig, libdiscid, libofa, ffmpeg, acoustidFingerprinter
+}:
 
 pythonPackages.buildPythonPackage rec {
   name = "picard-${version}";
@@ -11,6 +12,13 @@ pythonPackages.buildPythonPackage rec {
     md5 = "d1086687b7f7b0d359a731b1a25e7b66";
   };
 
+  postPatch = let
+    fpr = "${acoustidFingerprinter}/bin/acoustid_fpcalc";
+  in ''
+    sed -ri -e 's|(TextOption.*"acoustid_fpcalc"[^"]*")[^"]*|\1${fpr}|' \
+      picard/ui/options/fingerprinting.py
+  '';
+
   buildInputs = [
     pkgconfig
     ffmpeg