test: use DGR_TEST_GH_PATH to mock missing gh executable

Instead of destructively replacing the PATH on Windows to hide the `gh` executable—which caused Rust 1.77.2 to fail spawning `git` due to implicit extension resolution changes—this commit adds a `DGR_TEST_GH_PATH` environment variable for testing. The test now injects a nonexistent path to cleanly simulate a missing `gh` CLI without breaking access to system executables like `git`.

Author: mark-pro

src/core/gh.rs

@@ -4,7 +4,6 @@ use std::path::PathBuf;
 use std::process::{Command, ExitStatus, Output, Stdio};
 use std::thread;
 
-#[cfg(windows)]
 use std::env;
 
 use serde::Deserialize;
@@ -500,11 +499,19 @@ fn gh_command() -> io::Result<Command> {
 
 #[cfg(not(windows))]
 fn resolve_gh_executable() -> io::Result<PathBuf> {
+    if let Some(path) = env::var_os("DGR_TEST_GH_PATH") {
+        return Ok(PathBuf::from(path));
+    }
+
     Ok(PathBuf::from("gh"))
 }
 
 #[cfg(windows)]
 fn resolve_gh_executable() -> io::Result<PathBuf> {
+    if let Some(path) = env::var_os("DGR_TEST_GH_PATH") {
+        return Ok(PathBuf::from(path));
+    }
+
     let path = env::var_os("PATH").unwrap_or_default();
     let pathext = env::var_os("PATHEXT")
         .unwrap_or_else(|| ".COM;.EXE;.BAT;.CMD".into())

tests/pr.rs

@@ -5,7 +5,7 @@ use std::path::{Path, PathBuf};
 
 use serde_json::json;
 use support::{
-    dgr_ok, dgr_ok_with_env, dgr_with_input_and_env, find_node, git_binary_path, git_ok,
+    dgr_ok, dgr_ok_with_env, dgr_with_input_and_env, find_node, git_ok,
     git_stdout, initialize_main_repo, install_fake_executable, load_events_json, load_state_json,
     path_with_prepend, strip_ansi, with_temp_repo,
 };
@@ -870,16 +870,8 @@ fn pr_reports_missing_gh_cli() {
         dgr_ok(repo, &["init"]);
         dgr_ok(repo, &["branch", "feat/auth"]);
 
-        let bin_dir = repo.join("fake-bin");
-        let git_path = git_binary_path();
-        install_fake_executable(
-            &bin_dir,
-            "git",
-            &format!("#!/bin/sh\nset -eu\nexec \"{}\" \"$@\"\n", git_path),
-        );
-        let path = bin_dir.display().to_string();
-
-        let output = support::dgr_with_env(repo, &["pr"], &[("PATH", path.as_str())]);
+        let output =
+            support::dgr_with_env(repo, &["pr"], &[("DGR_TEST_GH_PATH", "/does/not/exist/gh")]);
 
         assert!(!output.status.success());
         let stderr = String::from_utf8(output.stderr).unwrap();