bug#31924: Tramp handler timeout with custom method

[Sheng Yang]

I am using tramp with a custom method, and the commit b70f885d seems to break it.

The usage is with yadm (https://yadm.io/), which prepares a bare git repo to host dotfiles. Here is a minimum script to reproduce the problem:

#!/bin/bash

# this file is /tmp/yadm.sh

shell_opts=""

  shell_path=""

  if [[ "$SHELL" =~ bash$ ]]; then

    shell_opts="--norc"

    shell_path="\w"

  elif [[ "$SHELL" =~ [cz]sh$ ]]; then

    shell_opts="-f"

    shell_path="%~"

  fi

  if [[ "$TERM" == "dumb" ]]; then

    yadm_prompt=" > "

  fi

  # echo "Entering yadm repo"

  PROMPT="$yadm_prompt" PS1="$yadm_prompt" "$SHELL" $shell_opts

  echo "Leaving yadm repo"

# end of yadm.sh

Start emacs with emacs -q, and evaluate the following

(require 'tramp)

(add-to-list 'tramp-methods

             '("yadm"

               (tramp-login-program "/tmp/yadm.sh")

               ;; setting the following is crucial

               (tramp-login-env

                (("SHELL")

                 ("/bin/sh")))

               (tramp-remote-shell "/bin/sh")

               (tramp-remote-shell-args ("-c"))

               (tramp-connection-timeout 10)))

(find-file "/yadm::.")

which will lead to a timeout.

Notes:

1. Note setting tramp-login-env with SHELL as "/bin/sh" is crucial for this method to work

2. My default shell is /usr/bin/zsh

3. The tramp buffer also has the mysterious "[?2004h" in the tramp buffer.

Please see log files with (setq tramp-verbose  10) in attachment.

Sheng Yang(杨圣), PhD student

Computer Science Department

University of Maryland, College Park

E-mail: styang@fastmail.com

E-mail (old but still used): yangsheng6810@gmail.com

tramp.log
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tramp-yadm.log
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