shell-wrapper: only overwrite $SHELL if it is pointing to the wrapper

Author: nzbr

utils/src/shell_wrapper.rs

@@ -18,7 +18,10 @@ fn real_main() -> anyhow::Result<()> {
     let shell = read_link(exe_dir.join("shell")).context("when locating the wrapped shell")?;
 
     // Set the SHELL environment variable to the wrapped shell instead of the wrapper
-    env::set_var("SHELL", &shell);
+    let shell_env = env::var_os("SHELL").unwrap_or_default();
+    if shell_env == exe {
+        env::set_var("SHELL", &shell);
+    }
 
     // Skip if environment was already set
     if env::var_os("__NIXOS_SET_ENVIRONMENT_DONE") != Some("1".into()) {