Add meta for elixir & rebar.

Signed-off-by: Moritz Ulrich <moritz@tarn-vedra.de>

pkgs/development/interpreters/elixir/default.nix

@@ -17,4 +17,19 @@ stdenv.mkDerivation {
       --replace '$(shell echo `pwd`/rebar)' ${rebar}/bin/rebar \
       --replace "/usr/local" $out
   '';
+
+  meta = {
+    homepage = "http://elixir-lang.org/";
+    description = "Elixir is a functional, meta-programming aware language built on top of the Erlang VM.";
+
+    longDescription = ''
+      Elixir is a functional, meta-programming
+      aware language built on top of the Erlang VM. It is a dynamic
+      language with flexible syntax and macro support that leverages
+      Erlang's abilities to build concurrent, distributed and
+      fault-tolerant applications with hot code upgrades.p
+    '';
+
+    platforms = stdenv.lib.platforms.linux;
+  };
 }

pkgs/development/tools/build-managers/rebar/default.nix

@@ -15,4 +15,21 @@ stdenv.mkDerivation {
     mkdir -p $out/bin
     cp rebar $out/bin/rebar
   '';
+
+  meta = {
+    homepage = "https://github.com/rebar/rebar";
+    description = "Erlang build tool that makes it easy to compile and test Erlang applications, port drivers and releases.";
+
+    longDescription = ''
+      rebar is a self-contained Erlang script, so it's easy to
+      distribute or even embed directly in a project. Where possible,
+      rebar uses standard Erlang/OTP conventions for project
+      structures, thus minimizing the amount of build configuration
+      work. rebar also provides dependency management, enabling
+      application writers to easily re-use common libraries from a
+      variety of locations (git, hg, etc).
+      '';
+
+    platforms = stdenv.lib.platforms.linux;
+  };
 }