debugruntest: fix requires binary invocation for debugruntest .t tests

Summary:
When running `.t` integration tests using `debugruntest`, and those tests depend on some external binary, they have to be declared with teh `requires` keyword at the beginning of the test. Those external binaries can be invoked either by the "shell" in the `.t` tests or by hg/sl.

Before this diff a mechanism existed for calling external commands under `debugruntest`, but this only worked for those invoked via the `ui.system` method. This was possible since one of the methods ultimately called by `ui.system` was monkey-patched by `hg.py`. This diff does something similar for the `subprocess.run` method.

Reviewed By: quark-zju

Differential Revision: D41793101

fbshipit-source-id: dffb042791e3c4b9be9ae05a8b8586a4fe3f382d

eden/scm/edenscm/testing/ext/hg.py

@@ -13,6 +13,7 @@
 
 import io
 import os
+import subprocess
 import sys
 from functools import partial
 from typing import BinaryIO
@@ -206,7 +207,11 @@ def hg(stdin: BinaryIO, stdout: BinaryIO, stderr: BinaryIO, env: Env) -> int:
     try:
         with shellenv(
             env, stdin=stdin, stdout=stdout, stderr=stderr
-        ), extensions.wrappedfunction(util, "rawsystem", rawsystem):
+        ), extensions.wrappedfunction(
+            util, "rawsystem", rawsystem
+        ), extensions.wrappedfunction(
+            subprocess, "run", _patchedsubprun
+        ):
             bindings.identity.resetdefault()
 
             encoding.setfromenviron()
@@ -255,6 +260,16 @@ def _rawsystem(
     return res.exitcode
 
 
+def _patchedsubprun(orig, args, **kwargs):
+    if os.name == "nt" and args:
+        # append ".bat" to args[0]
+        arg0bat = f"{args[0]}.bat"
+        paths = os.getenv("PATH", "").split(os.pathsep)
+        if any(os.path.exists(os.path.join(p, arg0bat)) for p in paths):
+            args[0] = arg0bat
+    return orig(args, **kwargs)
+
+
 def _execpython(path):
     """execute python code at path, return its globals"""
     with open(path, "r") as f: