nix: Move shell hook: default.nix -> shell.nix and set custom prompt.

When using multiple dev envs with nix-shell it's good to have a unique
shell propt to distinguish them.

default.nix

@@ -156,18 +156,6 b' let'
         then "${pkgs.glibcLocales}/lib/locale/locale-archive"
         else "";
 
-      # Somewhat snappier setup of the development environment
-      # TODO: move into shell.nix
-      # TODO: think of supporting a stable path again, so that multiple shells
-      #       can share it.
-      shellHook = ''
-        tmp_path=$(mktemp -d)
-        export PATH="$tmp_path/bin:$PATH"
-        export PYTHONPATH="$tmp_path/${self.python.sitePackages}:$PYTHONPATH"
-        mkdir -p $tmp_path/${self.python.sitePackages}
-        python setup.py develop --prefix $tmp_path --allow-hosts ""
-      '' + linkNodeAndBowerPackages;
-
       preCheck = ''
         export PATH="$out/bin:$PATH"
       '';

shell.nix

@@ -27,13 +27,13 b' let'
 
   hasVcsserver = !isNull vcsserver;
 
-  enterprise = import ./default.nix {
+  enterprise-ce = import ./default.nix {
     inherit pkgs doCheck;
   };
 
-  pythonPackages = enterprise.pythonPackages;
+  ce-pythonPackages = enterprise-ce.pythonPackages;
 
-in enterprise.override (attrs: {
+in enterprise-ce.override (attrs: {
   # Avoid that we dump any sources into the store when entering the shell and
   # make development a little bit more convenient.
   src = null;
@@ -41,17 +41,30 b' in enterprise.override (attrs: {'
   buildInputs =
     attrs.buildInputs ++
     pkgs.lib.optionals (hasVcsserver) vcsserver.propagatedNativeBuildInputs ++
-    (with pythonPackages; [
+    (with ce-pythonPackages; [
       bumpversion
       invoke
       ipdb
     ]);
 
-  shellHook = attrs.shellHook +
+  # Somewhat snappier setup of the development environment
+  # TODO: think of supporting a stable path again, so that multiple shells
+  #       can share it.
+  postShellHook = ''
+    # Custom prompt to distinguish from other dev envs.
+    export PS1="\n\[\033[1;32m\][CE-shell:\w]$\[\033[0m\] "
+
+    tmp_path=$(mktemp -d)
+    export PATH="$tmp_path/bin:$PATH"
+    export PYTHONPATH="$tmp_path/${ce-pythonPackages.python.sitePackages}:$PYTHONPATH"
+    mkdir -p $tmp_path/${ce-pythonPackages.python.sitePackages}
+    python setup.py develop --prefix $tmp_path --allow-hosts ""
+    '' + enterprise-ce.linkNodeAndBowerPackages +
     pkgs.lib.strings.optionalString (hasVcsserver) ''
       # Setup the vcsserver development egg.
       pushd ${vcsserverAbsPath}
       python setup.py develop --prefix $tmp_path --allow-hosts ""
       popd
     '';
+
 })