fix: keep cmd.exe off the terminal under WSL

Reading the Windows variables through cmd.exe let it consume the answer typed at the first prompt: a WSL run exited 0 with nothing installed.

install.ps1

@@ -8,7 +8,7 @@ param(
 
 $ErrorActionPreference = "Stop"
 $defaultInstallUrl = "https://raw.githubusercontent.com/Abdess/retrobios/main/install.py"
-$defaultInstallSha256 = "12b0c9b711955a664941529f4fef36a55799472d9788d43ab1988a15d31ce452"
+$defaultInstallSha256 = "7e74935ae51bf8b0076f637bc640b33f0ca774bec065df56080a0321fa292820"
 $maximumInstallerBytes = 2MB
 $installerExit = 0
 $installer = if ($PSScriptRoot) { Join-Path $PSScriptRoot "install.py" } else { $null }

install.py

@@ -467,9 +467,11 @@ def _enter_wsl() -> None:
         if os.environ.get(variable):
             continue
         try:
+            # No stdin: cmd.exe inherited the terminal and swallowed the
+            # answer typed at the first prompt.
             result = subprocess.run(
                 ["cmd.exe", "/c", f"echo %{variable}%"],
-                capture_output=True, text=True, timeout=10,
+                capture_output=True, text=True, timeout=10, stdin=subprocess.DEVNULL,
                 cwd="/mnt/c" if Path("/mnt/c").is_dir() else None,
             )
         except (OSError, subprocess.SubprocessError):

install.sh

@@ -18,7 +18,7 @@ esac
 TEMP_INSTALLER=""
 TEMP_DIRECTORY=""
 DEFAULT_INSTALL_URL="https://raw.githubusercontent.com/Abdess/retrobios/main/install.py"
-DEFAULT_INSTALL_SHA256="12b0c9b711955a664941529f4fef36a55799472d9788d43ab1988a15d31ce452"
+DEFAULT_INSTALL_SHA256="7e74935ae51bf8b0076f637bc640b33f0ca774bec065df56080a0321fa292820"
 MAX_INSTALLER_BYTES=2097152
 
 cleanup() {

tests/test_install.py

@@ -2812,7 +2812,10 @@ class WindowsSeenFromWsl(unittest.TestCase):
     def test_the_windows_variables_are_read_through_cmd(self):
         answers = {"USERPROFILE": "C:\\Users\\me", "APPDATA": "C:\\Users\\me\\AppData\\Roaming"}
 
-        def cmd(argv, **_kwargs):
+        def cmd(argv, **kwargs):
+            # cmd.exe must not read the terminal: it swallowed the answer
+            # typed at the first prompt.
+            self.assertIs(kwargs.get("stdin"), subprocess.DEVNULL)
             name = argv[-1].split("%")[1]
             return subprocess.CompletedProcess(argv, 0, answers.get(name, f"%{name}%") + "\r\n", "")