* fetchsvn' now requires the MD5 hash (as computed by nix-hash') of

the tree being fetched from a Subversion repository.  The revision
  number is now optional (and defaults to HEAD).

  This makes `fetchsvn' more pure.  First, a URL/revision tuple does
  not uniquely identify a file resource, since the repository itself
  might change.  Second, `svn:external' attributes can cause arbitrary
  resources to be exported.

  A script `nix-prefetch-svn' has been provided to determine the hash
  of a URL.

svn path=/nixpkgs/trunk/; revision=938

pkgs/build-support/fetchsvn/default.nix

@@ -1,7 +1,9 @@
-{stdenv, subversion}: {url, rev}: stdenv.mkDerivation {
-  name = "svn-checkout";
+{stdenv, subversion, nix}: {url, rev ? "HEAD", md5}:
+
+stdenv.mkDerivation {
+  name = "svn-export";
   builder = ./builder.sh;
-  subversion = subversion;
-  url = url;
-  rev = rev;
+  buildInputs = [subversion nix];
+  id = md5;
+  inherit url rev md5;
 }