pkgs/shells: move extensions to subdirs

These are not reaal shells and should go into their parent shell
directory.

pkgs/shells/bash/bash-completion/default.nix

@@ -0,0 +1,25 @@
+{ stdenv, fetchurl }:
+
+stdenv.mkDerivation rec {
+  name = "bash-completion-${version}";
+  version = "2.8";
+
+  src = fetchurl {
+    url = "https://github.com/scop/bash-completion/releases/download/${version}/${name}.tar.xz";
+    sha256 = "0kgmflrr1ga9wfk770vmakna3nj46ylb5ky9ipd0v2k9ymq5a7y0";
+  };
+
+  doCheck = true;
+
+  prePatch = stdenv.lib.optionalString stdenv.isDarwin ''
+    sed -i -e 's/readlink -f/readlink/g' bash_completion completions/*
+  '';
+
+  meta = with stdenv.lib; {
+    homepage = https://github.com/scop/bash-completion;
+    description = "Programmable completion for the bash shell";
+    license = licenses.gpl2Plus;
+    platforms = platforms.unix;
+    maintainers = [ maintainers.peti ];
+  };
+}

pkgs/shells/bash/nix-bash-completions/default.nix

@@ -0,0 +1,36 @@
+{ stdenv, fetchFromGitHub }:
+
+stdenv.mkDerivation rec {
+  version = "0.6.5";
+  name = "nix-bash-completions-${version}";
+
+  src = fetchFromGitHub {
+    owner = "hedning";
+    repo = "nix-bash-completions";
+    rev = "v${version}";
+    sha256 = "10f70jw81vky52s3fidf7vzl725fihiypsw39825wnkpynayhmrg";
+  };
+
+  # To enable lazy loading via. bash-completion we need a symlink to the script
+  # from every command name.
+  installPhase = ''
+    commands=$(
+      function complete() { shift 2; echo "$@"; }
+      shopt -s extglob
+      source _nix
+    )
+    install -Dm444 -t $out/share/bash-completion/completions _nix
+    cd $out/share/bash-completion/completions
+    for c in $commands; do
+      ln -s _nix $c
+    done
+  '';
+
+  meta = with stdenv.lib; {
+    homepage = https://github.com/hedning/nix-bash-completions;
+    description = "Bash completions for Nix, NixOS, and NixOps";
+    license = licenses.bsd3;
+    platforms = platforms.all;
+    maintainers = with maintainers; [ hedning ];
+  };
+}