From 398c4136c2a963a38b8d7664c47f2bd8c60e86c3 Mon Sep 17 00:00:00 2001
From: Graham Christensen <graham@grahamc.com>
Date: Mon, 31 Mar 2025 21:35:15 -0400
Subject: [PATCH] Improve and fix the error message when a file is not tracked
 by Git

(cherry picked from commit 62e2304891375f642ac7b52358d36455ce99171a)
---
 src/libfetchers/git.cc | 20 +++++++++++++++-----
 1 file changed, 15 insertions(+), 5 deletions(-)

diff --git a/src/libfetchers/git.cc b/src/libfetchers/git.cc
index f46334d30..5684583cd 100644
--- a/src/libfetchers/git.cc
+++ b/src/libfetchers/git.cc
@@ -534,11 +534,21 @@ struct GitInputScheme : InputScheme
 
     static MakeNotAllowedError makeNotAllowedError(std::string url)
     {
-        return [url{std::move(url)}](const CanonPath & path) -> RestrictedPathError
-        {
-            if (nix::pathExists(path.abs()))
-                return RestrictedPathError("access to path '%s' is forbidden because it is not under Git control; maybe you should 'git add' it to the repository '%s'?", path, url);
-            else
+        return [url{std::move(url)}](const CanonPath & path) -> RestrictedPathError {
+            if (nix::pathExists(url + "/" + path.abs())) {
+                auto relativePath = path.rel(); // .makeRelative(CanonPath("/"));
+
+                return RestrictedPathError(
+                    "'%s' is not tracked by Git.\n"
+                    "\n"
+                    "To use '%s', stage it in the Git repository at '%s':\n"
+                    "\n"
+                    "git add %s",
+                    relativePath,
+                    relativePath,
+                    url,
+                    relativePath);
+            } else
                 return RestrictedPathError("path '%s' does not exist in Git repository '%s'", path, url);
         };
     }