From a83caea82953d5f581128baf559cacaec6e0d2a2 Mon Sep 17 00:00:00 2001
From: Alex Shabalin <alex.shabalin@tweag.io>
Date: Wed, 17 Nov 2021 16:09:36 +0100
Subject: [PATCH] Set IN_NIX3_SHELL env variable in "nix shell"

Solving issue https://github.com/NixOS/nix/issues/3862

Co-authored-by: Alexander Bantyev <balsoft@balsoft.ru>
---
 src/nix/run.cc | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/nix/run.cc b/src/nix/run.cc
index b01fdebaa..8e0eba00b 100644
--- a/src/nix/run.cc
+++ b/src/nix/run.cc
@@ -120,6 +120,7 @@ struct CmdShell : InstallablesCommand, MixEnvironment
         }
 
         setenv("PATH", concatStringsSep(":", unixPath).c_str(), 1);
+        setenv("IN_NIX3_SHELL", "1", 1);
 
         Strings args;
         for (auto & arg : command) args.push_back(arg);