refactor: consolidate read_tty_line into bot_bottle/util.py

Remove the private _read_tty_line duplicate from backend/__init__.py and
the local definition from cli/_common.py. Both now import from the
shared bot_bottle.util module.

bot_bottle/backend/__init__.py

@@ -46,6 +46,7 @@ from ..agent_provider import AgentProvisionPlan, get_provider, build_agent_provi
 from ..egress import EgressPlan
 from ..git_gate import GitGatePlan
 from ..log import die, info, warn
+from ..util import read_tty_line
 from ..manifest import Manifest, ManifestIndex
 from ..supervise import SupervisePlan
 from ..util import expand_tilde
@@ -668,15 +669,6 @@ def get_bottle_backend(
     return backends[resolved]
 
 
-def _read_tty_line() -> str:
-    """Read a line from /dev/tty, falling back to stdin."""
-    try:
-        with open("/dev/tty", "r", encoding="utf-8") as tty:
-            return tty.readline().rstrip("\n")
-    except OSError:
-        return sys.stdin.readline().rstrip("\n")
-
-
 def _platform_vm_suggestion() -> str:
     """Platform-appropriate VM backend name for install suggestions."""
     return "macos-container" if sys.platform == "darwin" else "firecracker"
@@ -733,7 +725,7 @@ def _auto_select_backend() -> str:
         "bot-bottle: choice [i/d/q]: "
     )
     sys.stderr.flush()
-    reply = _read_tty_line().strip().lower()
+    reply = read_tty_line().strip().lower()
     if reply == "d":
         return "docker"
     if reply == "i":

bot_bottle/cli/_common.py

@@ -3,18 +3,10 @@
 from __future__ import annotations
 
 import os
-import sys
 from pathlib import Path
 
+from ..util import read_tty_line
+
 PROG = "cli.py"
 USER_CWD = os.getcwd()
 REPO_DIR = str(Path(__file__).resolve().parent.parent.parent)
-
-
-def read_tty_line() -> str:
-    """Mirror `IFS= read -r REPLY </dev/tty`. Falls back to stdin."""
-    try:
-        with open("/dev/tty", "r", encoding="utf-8") as tty:
-            return tty.readline().rstrip("\n")
-    except OSError:
-        return sys.stdin.readline().rstrip("\n")

bot_bottle/util.py

@@ -7,6 +7,7 @@ from __future__ import annotations
 
 import ipaddress
 import os
+import sys
 
 
 def is_ip_literal(value: str) -> bool:
@@ -17,6 +18,15 @@ def is_ip_literal(value: str) -> bool:
     return True
 
 
+def read_tty_line() -> str:
+    """Mirror `IFS= read -r REPLY </dev/tty`. Falls back to stdin."""
+    try:
+        with open("/dev/tty", "r", encoding="utf-8") as tty:
+            return tty.readline().rstrip("\n")
+    except OSError:
+        return sys.stdin.readline().rstrip("\n")
+
+
 def expand_tilde(path: str) -> str:
     """Expand a leading '~' to $HOME. Leaves paths without a leading
     tilde unchanged. Falls back to the empty string if $HOME is unset

tests/unit/test_backend_selection.py

@@ -66,7 +66,7 @@ class TestGetBottleBackend(unittest.TestCase):
                  "macos-container": _FakeBackend("macos-container", False),
                  "docker": _FakeBackend("docker", True),
              }), \
-             patch.object(backend_mod, "_read_tty_line", return_value="d"):
+             patch.object(backend_mod, "read_tty_line", return_value="d"):
             b = get_bottle_backend()
         self.assertEqual("docker", b.name)
 
@@ -136,7 +136,7 @@ class TestGetBottleBackend(unittest.TestCase):
                  "macos-container": _FakeBackend("macos-container", False),
                  "docker": _FakeBackend("docker", True),
              }), \
-             patch.object(backend_mod, "_read_tty_line", return_value="q"), \
+             patch.object(backend_mod, "read_tty_line", return_value="q"), \
              patch.object(backend_mod, "die", side_effect=SystemExit("die")):
             with self.assertRaises(SystemExit):
                 get_bottle_backend()
@@ -159,7 +159,7 @@ class TestGetBottleBackend(unittest.TestCase):
                  "macos-container": _FakeBackend("macos-container", False),
                  "docker": _FakeBackend("docker", True),
              }), \
-             patch.object(backend_mod, "_read_tty_line", return_value="i"), \
+             patch.object(backend_mod, "read_tty_line", return_value="i"), \
              patch.object(backend_mod, "_print_vm_install_instructions") as mock_inst, \
              patch.object(backend_mod, "die", side_effect=SystemExit("die")):
             with self.assertRaises(SystemExit):
@@ -168,26 +168,26 @@ class TestGetBottleBackend(unittest.TestCase):
 
 
 class TestReadTtyLine(unittest.TestCase):
-    """Unit tests for the _read_tty_line helper."""
+    """Unit tests for the shared read_tty_line helper in bot_bottle.util."""
 
     def test_reads_from_dev_tty(self):
         from unittest.mock import mock_open
-        from bot_bottle.backend import _read_tty_line
+        from bot_bottle.util import read_tty_line
 
         m = mock_open(read_data="hello\n")
         with patch("builtins.open", m):
-            result = _read_tty_line()
+            result = read_tty_line()
         self.assertEqual("hello", result)
         m.assert_called_once_with("/dev/tty", "r", encoding="utf-8")
 
     def test_falls_back_to_stdin_on_oserror(self):
         import io
-        from bot_bottle.backend import _read_tty_line
+        from bot_bottle.util import read_tty_line
         import sys as _sys
 
         with patch("builtins.open", side_effect=OSError("no tty")), \
              patch.object(_sys, "stdin", io.StringIO("world\n")):
-            result = _read_tty_line()
+            result = read_tty_line()
         self.assertEqual("world", result)