From d678b071d69569786db4a4cc8110ee0cd4496e2f Mon Sep 17 00:00:00 2001
From: Oleksandr Knyshuk <olk@disr.it>
Date: Thu, 17 Jul 2025 17:26:56 +0200
Subject: [PATCH] Make nix help shell work by handling aliases properly

Previously, `nix help shell` failed with "Nix has no subcommand 'shell'" despite `nix shell --help`
working correctly. This happened because the `shell` command is actually an alias for `env shell`,
and the help system wasn't resolving aliases when looking up documentation.

This patch modifies the `showHelp` function to check for and resolve aliases before generating the
manpage name, ensuring that shorthand commands like `shell` get proper help documentation.

Closes: #13431
---
 src/nix/main.cc | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/src/nix/main.cc b/src/nix/main.cc
index 6144f746f..502e04e60 100644
--- a/src/nix/main.cc
+++ b/src/nix/main.cc
@@ -212,6 +212,14 @@ struct NixArgs : virtual MultiCommand, virtual MixCommonArgs, virtual RootArgs
    lowdown. */
 static void showHelp(std::vector<std::string> subcommand, NixArgs & toplevel)
 {
+    // Check for aliases if subcommand has exactly one element
+    if (subcommand.size() == 1) {
+        auto alias = toplevel.aliases.find(subcommand[0]);
+        if (alias != toplevel.aliases.end()) {
+            subcommand = alias->second.replacement;
+        }
+    }
+
     auto mdName = subcommand.empty() ? "nix" : fmt("nix3-%s", concatStringsSep("-", subcommand));
 
     evalSettings.restrictEval = false;