mkShell: Control devShell and override prompt

pkgs/build-support/mkshell/default.nix

@@ -2,6 +2,7 @@
   lib,
   stdenv,
   buildEnv,
+  devShellTools,
 }:
 
 # A special kind of derivation that is only meant to be consumed by the
@@ -16,6 +17,7 @@
   nativeBuildInputs ? [ ],
   propagatedBuildInputs ? [ ],
   propagatedNativeBuildInputs ? [ ],
+  passthru ? { },
   ...
 }@attrs:
 let
@@ -42,6 +44,7 @@ let
 in
 
 stdenv.mkDerivation (
+  finalAttrs:
   {
     inherit name;
 
@@ -68,6 +71,33 @@ stdenv.mkDerivation (
     '';
 
     preferLocalBuild = true;
+
+    passthru = {
+      devShell =
+        let
+          inherit (finalAttrs.finalPackage) drvAttrs;
+        in
+        devShellTools.buildShellEnv {
+          inherit drvAttrs;
+
+          # The default prefix is "build shell", but this shell is not derived
+          # directly from a derivation, so we set a more generic title.
+          promptPrefix = "nix";
+
+          # Change the default name
+          promptName =
+            if
+              # name was passed originally
+              attrs ? name
+              # or with overrideAttrs
+              || drvAttrs.name != "nix-shell"
+            then
+              null
+            else
+              "mkShell";
+        };
+    }
+    // passthru;
   }
   // rest
 )