Server(feat[tmux_bin]): Add configurable tmux binary path

why: shutil.which("tmux") is hardcoded in tmux_cmd and Server. No way
to use wemux, byobu, or a custom-built tmux. tmuxinator supports
tmux_command config key including wemux module.
what:
- Add tmux_bin keyword arg to tmux_cmd.__init__ (backward compatible)
- Add tmux_bin parameter to Server.__init__ with pathlib.Path support
- Thread tmux_bin through Server.cmd(), Server.raise_if_dead(), and
  neo.fetch_objs()
- Session/Window/Pane inherit via server.cmd() delegation
- Add tests for default, custom path, and invalid path scenarios

Author: tony

src/libtmux/common.py

@@ -248,12 +248,12 @@ class tmux_cmd:
         Renamed from ``tmux`` to ``tmux_cmd``.
     """
 
-    def __init__(self, *args: t.Any) -> None:
-        tmux_bin = shutil.which("tmux")
-        if not tmux_bin:
+    def __init__(self, *args: t.Any, tmux_bin: str | None = None) -> None:
+        resolved = tmux_bin or shutil.which("tmux")
+        if not resolved:
             raise exc.TmuxCommandNotFound
 
-        cmd = [tmux_bin]
+        cmd = [resolved]
         cmd += args  # add the command arguments to cmd
         cmd = [str(c) for c in cmd]
 

src/libtmux/neo.py

@@ -319,7 +319,10 @@ def fetch_objs(
             },
         )
 
-    proc = tmux_cmd(*tmux_cmds)  # output
+    proc = tmux_cmd(
+        *tmux_cmds,
+        tmux_bin=server.tmux_bin if server is not None else None,
+    )
 
     if proc.stderr:
         raise exc.LibTmuxException(proc.stderr)

src/libtmux/server.py

@@ -127,6 +127,8 @@ class Server(
     """For option management."""
     default_hook_scope: OptionScope | None = OptionScope.Server
     """For hook management."""
+    tmux_bin: str | None = None
+    """Custom path to tmux binary. Falls back to ``shutil.which("tmux")``."""
 
     def __init__(
         self,
@@ -136,9 +138,11 @@ def __init__(
         colors: int | None = None,
         on_init: t.Callable[[Server], None] | None = None,
         socket_name_factory: t.Callable[[], str] | None = None,
+        tmux_bin: str | pathlib.Path | None = None,
         **kwargs: t.Any,
     ) -> None:
         EnvironmentMixin.__init__(self, "-g")
+        self.tmux_bin = str(tmux_bin) if tmux_bin else None
         self._windows: list[WindowDict] = []
         self._panes: list[PaneDict] = []
 
@@ -220,8 +224,8 @@ def raise_if_dead(self) -> None:
         ...     print(type(e))
         <class 'subprocess.CalledProcessError'>
         """
-        tmux_bin = shutil.which("tmux")
-        if tmux_bin is None:
+        resolved = self.tmux_bin or shutil.which("tmux")
+        if resolved is None:
             raise exc.TmuxCommandNotFound
 
         cmd_args: list[str] = ["list-sessions"]
@@ -232,7 +236,7 @@ def raise_if_dead(self) -> None:
         if self.config_file:
             cmd_args.insert(0, f"-f{self.config_file}")
 
-        subprocess.check_call([tmux_bin, *cmd_args])
+        subprocess.check_call([resolved, *cmd_args])
 
     #
     # Command
@@ -308,7 +312,7 @@ def cmd(
 
         cmd_args = ["-t", str(target), *args] if target is not None else [*args]
 
-        return tmux_cmd(*svr_args, *cmd_args)
+        return tmux_cmd(*svr_args, *cmd_args, tmux_bin=self.tmux_bin)
 
     @property
     def attached_sessions(self) -> list[Session]:

tests/test_server.py

@@ -5,6 +5,7 @@
 import logging
 import os
 import pathlib
+import shutil
 import subprocess
 import time
 import typing as t
@@ -414,3 +415,24 @@ def test_new_session_start_directory_pathlib(
     actual_path = str(pathlib.Path(active_pane.pane_current_path).resolve())
     expected_path = str(user_path.resolve())
     assert actual_path == expected_path
+
+
+def test_tmux_bin_default(server: Server) -> None:
+    """Default tmux_bin is None, falls back to shutil.which."""
+    assert server.tmux_bin is None
+
+
+def test_tmux_bin_custom_path() -> None:
+    """Custom tmux_bin path is used for commands."""
+    tmux_path = shutil.which("tmux")
+    assert tmux_path is not None
+    s = Server(tmux_bin=tmux_path)
+    # Should work identically to default
+    assert s.tmux_bin == tmux_path
+
+
+def test_tmux_bin_invalid_path() -> None:
+    """Invalid tmux_bin raises on command execution."""
+    s = Server(tmux_bin="/nonexistent/tmux")
+    with pytest.raises(FileNotFoundError):
+        s.cmd("list-sessions")