[gnu-emacs-elpa] / multishell.el

;;; multishell.el --- facilitate multiple local and remote shell buffers

;; Copyright (C) 1999-2016 Free Software Foundation, Inc. and Ken Manheimer

;; Author: Ken Manheimer <ken.manheimer@gmail.com>
;; Version: 1.0.10
;; Created: 1999 -- first public availability
;; Keywords: processes
;; URL: https://github.com/kenmanheimer/EmacsMultishell
;;
;;; Commentary:
;;
;; Easily use and navigate multiple shell buffers, including remote shells.
;; Fundamentally, multishell is the function `multishell-pop-to-shell' -
;; a la `pop-to-buffer' - plus a keybinding. Together, they enable you to:
;;
;; * Get to the input point from wherever you are in a shell buffer,
;;   ... or to any of your shell buffers, from anywhere inside emacs.
;;
;; * Use universal arguments to launch and choose among alternate shell buffers,
;;   ... and change which is the current default.
;;
;; * Easily restart disconnected shells, or shells from prior sessions
;;   ... the latter from Emacs builtin savehist minibuf history persistence
;;
;; * Append a path to a new shell name to launch a shell in that directory,
;;   ... and use a path with Emacs tramp syntax to launch a remote shell -
;;   for example:
;;
;;   * `#root/sudo:root@localhost:/etc` for a buffer named "*#root*" with a
;;     root shell starting in /etc.
;;
;;   * `/ssh:example.net:` for a shell buffer in your homedir on example.net.
;;     The buffer will be named "*example.net*".
;;
;;   * `#ex/ssh:example.net|sudo:root@example.net:/var/log` for a root shell
;;     starting in /var/log on example.net named "*#ex*".
;;
;;   * 'interior/ssh:gateway.corp.com|ssh:interior.corp.com:' to go via
;;     gateway.corp.com to your homedir on interior.corp.com.  The buffer
;;     will be named "*interior*". You could append a sudo hop, and so on.
;;
;; * Thanks to tramp, file visits from the shell will seamlessly be in
;;   the auspices of the target account, and relative to the current
;;   directory, on the host where the shell is running.
;;
;; * Manage your list of shells, current and past, as a collection.
;;
;; See the `multishell-pop-to-shell` docstring for details.
;;
;; Customize-group `multishell' to select and activate a keybinding and set
;; various behaviors. Customize-group `savehist' to preserve buffer
;; names/paths across emacs restarts.
;;
;; Please use
;; [the multishell repository](https://github.com/kenmanheimer/EmacsMultishell)
;; issue tracker to report problems, suggestions, etc, and see that
;; repository for a bit more documentation.
;;
;; Change Log:
;;
;; * 2016-01-30 1.0.10 Ken Manheimer:
;;   - shake out some initial multishell-list glitches:
;;     - Delete shell buffer, if present, when deleting an entry.
;;       (Offer to) delete shell buffer, if present, when deleting an
;;       entry. Rely on the default active-shell deletion prompting
;;       for confirmation, supplementing with our own confirmation
;;       for inactive shell buffers.
;;     - Set recency (numeric rank) as initial sort field
;;     - Recompute list on any operation that affects it, and try to
;;       preserve stability. (Still needs work.)
;; * 2016-01-30 1.0.9 Ken Manheimer:
;;   - Add multishell-list for managing the collection of current and
;;     history-registered shells: edit, delete, and switch/pop to entries.
;;     Easy access by invoking `multishell-pop-to-shell' from in the
;;     `multishell-pop-to-shell' universal arg prompts.
;;   - Duplicate existing shell buffer names in completions, for distinction.
;;   - Add paths to buffers started without one, when multishell history dir
;;     tracking is enabled.
;;   - Major code cleanup:
;;     - Simplify multishell-start-shell-in-buffer, in particular using
;;       shell function, rather than unnecessarily going underneath it.
;;     - Establish multishell-name-from-entry as canonical name resolver.
;;     - Fallback to eval-after-load in emacs versions that lack
;;       with-eval-after-load (eg, emacs 23).
;;     - save-match-data, where match-string is used
;;     - resituate some helpers
;; * 2016-01-24 1.0.8 Ken Manheimer:
;;   - Work around the shell/tramp mishandling of remote+sudo+homedir problem!
;;     The work around is clean and simple, basically using high-level `cd'
;;     API and not messing with the low-level default-directory setting.
;;     (Turns out the problem was not in my local config. Good riddance to the
;;     awkward failure handler!)
;;   - Clean up code resolving the destination shell, starting to document the
;;     decision tree in the process. See getting-to-a-shell.md in the
;;     multishell repository, https://github.com/kenmanheimer/EmacsMultishell
;;   - There may be some shake-out on resolving the destination shell, but
;;     this release gets the fundamental functionality soundly in place.
;; * 2016-01-23 1.0.7 Ken Manheimer:
;;   - Remove notes about tramp remote+sudo+homedir problem. Apparently it's
;;     due to something in my local site configuration (happens with -q but
;;     not -Q).
;; * 2016-01-22 1.0.6 Ken Manheimer:
;;   - Add multishell-version function.
;;   - Tweak commentary/comments/docstrings.
;;   - Null old multishell-buffer-name-history var, if present.
;; * 2016-01-16 1.0.5 Ken Manheimer:
;;   - History now includes paths, when designated.
;;   - Actively track current directory in history entries that have a path.
;;     Custom control: multishell-history-entry-tracks-current-directory
;;   - Offer to remove shell's history entry when buffer is killed.
;;     (Currently the only UI mechanism to remove history entries.)
;;   - Fix - prevent duplicate entries for same name but different paths
;;   - Fix - recognize and respect tramp path syntax to start in home dir
;;   - Simplify history var name, migrate existing history if any from old name
;; * 2016-01-04 1.0.4 Ken Manheimer - Released to ELPA
;; * 2016-01-02 Ken Manheimer - working on this in public, but not yet released.
;;
;; TODO and Known Issues:
;;
;; * Resolve multishell-list sort glitches:
;;   - Fix config so multishell-list-revert-buffer-kludge is not needed
;;   - Make multishell-list-edit-entry in-place, so changed entries recency
;;     doesn't change.
;;   - Fill in kill-buffer prompting gaps, eg if default live-process
;;     prompts are inhibited.
;; * Add custom shell launch prep actions
;;   - for, eg, port knocking, interface activations
;;   - shell commands to execute when shell name or path matches a regexp
;;   - list of (regexp, which - name, path, or both, command)
;; * Adapt multishell-list facilities for all-completions
;;   - See info on minibuffer-completion-help, display-completion-list
;;   - implement markup for mouse selection
;; * Investigate whether we can recognize and provide for failed hops.
;;   - Tramp doesn't provide useful reactions for any hop but the first
;;   - Might be stuff we can do to detect and convey failures?
;;   - Might be no recourse but to seek tramp changes.
;; * Try minibuffer field boundary at beginning of tramp path, to see whether
;;   the field boundary magically enables tramp path completion.

;;; Code:

(require 'comint)
(require 'shell)
(require 'savehist)
(require 'multishell-list)

(defvar multishell-version "1.0.10")
(defun multishell-version (&optional here)
  "Return string describing the loaded multishell version."
  (interactive "P")
  (let ((msg (concat "Multishell " multishell-version)))
    (if here (insert msg)
      (if (called-interactively-p 'interactive)
          (message "%s" msg)
        msg))))

(defgroup multishell nil
  "Allout extension that highlights outline structure graphically.

Customize `allout-widgets-auto-activation' to activate allout-widgets
with allout-mode."
  :group 'shell)

(defcustom multishell-command-key "\M- "
  "The key to use if `multishell-activate-command-key' is true.

You can instead manually bind `multishell-pop-to-shell` using emacs
lisp, eg: (global-set-key \"\\M- \" 'multishell-pop-to-shell)."
  :type 'key-sequence
  :group 'multishell)

(defvar multishell--responsible-for-command-key nil
  "Coordination for multishell key assignment.")
(defun multishell-activate-command-key-setter (symbol setting)
  "Implement `multishell-activate-command-key' choice."
  (set-default 'multishell-activate-command-key setting)
  (when (or setting multishell--responsible-for-command-key)
    (multishell-implement-command-key-choice (not setting))))
(defun multishell-implement-command-key-choice (&optional unbind)
  "If settings dicate, implement binding of multishell command key.

If optional UNBIND is true, globally unbind the key.

* `multishell-activate-command-key' - Set this to get the binding or not.
* `multishell-command-key' - The key to use for the binding, if appropriate."
  (cond (unbind
         (when (and (boundp 'multishell-command-key) multishell-command-key)
           (global-unset-key multishell-command-key)))
        ((not (and (boundp 'multishell-activate-command-key)
                   (boundp 'multishell-command-key)))
         nil)
        ((and multishell-activate-command-key multishell-command-key)
         (setq multishell--responsible-for-command-key t)
         (global-set-key multishell-command-key 'multishell-pop-to-shell))))

(defcustom multishell-activate-command-key nil
  "Set this to impose the `multishell-command-key' binding.

You can instead manually bind `multishell-pop-to-shell` using emacs
lisp, eg: (global-set-key \"\\M- \" 'multishell-pop-to-shell)."
  :type 'boolean
  :set 'multishell-activate-command-key-setter
  :group 'multishell)

;; Implement the key customization whenever the package is loaded:
(if (fboundp 'with-eval-after-load)
    (with-eval-after-load "multishell"
                          (multishell-implement-command-key-choice))
  (eval-after-load "multishell"
    (multishell-implement-command-key-choice)))

(defcustom multishell-pop-to-frame nil
  "*If non-nil, jump to a frame already showing the shell, if another one is.

Otherwise, disregard already-open windows on the shell if they're
in another frame, and open a new window on the shell in the
current frame.

\(Use `pop-up-windows' to change multishell other-window vs
current-window behavior.)"
  :type 'boolean
  :group 'multishell)

(defcustom multishell-history-entry-tracks-current-directory t
  "Maintain shell's current directory in its multishell history entry.

When set, the history entry for shells started with explicit
paths will track the shell's current working directory. (Explicit
paths will not be added to local shells started without one,
however.)

If `savehist-save-minibuffer-history' is enabled, the current
working directory of shells \(that were started with an explicit
path) will be conveyed between emacs sessions."
 :type 'boolean
 :group 'multishell)

(defvar multishell-history nil
  "Name/path entries, most recent first.")
;; Migrate the few pre 1.0.5 users to changed history var:
(when (and (not multishell-history)
           (boundp 'multishell-buffer-name-history)
           multishell-buffer-name-history)
  (setq multishell-history multishell-buffer-name-history
        multishell-buffer-name-history nil))

(defvar multishell-primary-name "*shell*"
  "Default shell name for un-modified multishell-pop-to-shell buffer target.

This is set by `multishell-pop-to-shell' as the current default,
when invoked with doubled universal argument.

If you want the designated primary that you have at the end of
one emacs session to be resumed at the next, customize
`savehist-additional-variables' to include the
`multishell-primary-name'.")

;; Multiple entries happen because completion also adds name to history.
(defun multishell-register-name-to-path (name path)
  "Add or replace entry associating NAME with PATH in `multishell-history'.

If NAME already had a PATH and new PATH is empty, retain the prior one.

Promote added/changed entry to the front of the list."
  ;; Add or promote to the front, tracking path changes in the process.
  (let* ((entries (multishell-history-entries name))
         (path (or path "")))
    (dolist (entry entries)
      (when (string= path "")
        ;; Retain explicit established path.
        (setq path (cadr (multishell-split-entry entry))))
      (setq multishell-history (delete entry multishell-history)))
    (setq multishell-history (push (concat name path)
                                   multishell-history))))

(defun multishell-history-entries (name)
  "Return `multishell-history' entry that starts with NAME, or nil if none."
  (let (got)
    (dolist (entry multishell-history)
      (when (and (string-equal name (multishell-name-from-entry entry))
                 (not (member entry got)))
        (setq got (cons entry got))))
    got))

;;;###autoload
(defun multishell-pop-to-shell (&optional arg name here)
  "Easily navigate to and within multiple shell buffers, local and remote.

Use a single `universal-argument' (\\[universal-argument]) to launch and choose between
nalternate shell buffers, and a doubled universal argument to also set your
choice as the ongoing default.  Append a path to a new shell name to launch
a shell in that directory, and use Emacs tramp syntax to launch a remote
shell. There is a shortcut to manage your list of current and
historical shells, collectively, using `multishell-list' - see below.

Customize-group `multishell' to set up a key binding and tweak behaviors.

Manage your collection of current and historical shells by
recursively invoking \\[multishell-pop-to-shell] at either of the
`multishell-pop-to-shell' universal argument prompts, or at any time via
\\[multishell-list]. Hit ? in the listing buffer for editing commands.

==== Basic operation:

 - If the current buffer is shell-mode (or shell-mode derived)
   buffer then focus is moved to the process input point.

   \(You can use a universal argument go to a different shell
   buffer when already in a buffer that has a process - see
   below.)

 - If not in a shell buffer (or with universal argument), go to a
   window that is already showing the (a) shell buffer, if any.

   In this case, the cursor is left in its prior position in the
   shell buffer. Repeating the command will then go to the
   process input point, per the first item in this list.

   We respect `pop-up-windows', so you can adjust it to set the
   other-buffer/same-buffer behavior.

 - Otherwise, start a new shell buffer, using the current
   directory as the working directory.

If a buffer with the resulting name exists and its shell process
was disconnected or otherwise stopped, it's resumed.

===== Universal arg to start and select between named shell buffers:

You can name alternate shell buffers to create or return to, by
prefixing your \\[multishell-pop-to-shell] invocation with single or double
`universal-argument', \\[universal-argument]:

 - With a single universal argument, prompt for the buffer name
   to use (without the asterisks that shell mode will put around
   the name), defaulting to 'shell'.

   Completion is available.

   This combination makes it easy to start and switch across
   multiple shell restarts.

 - A double universal argument will prompt for the name *and* set
   the default to that name, so the target shell becomes the
   primary.

   See `multishell-primary-name' for info about preserving the
   setting across emacs restarts.

 - Manage your collection of current and historical shells by
   recursively invoking \\[multishell-pop-to-shell] at either of the
   `multishell-pop-to-shell' universal argument prompts, or at any
   time via \\[multishell-list]. Hit ? in the listing buffer for
   editing commands.

===== Select starting directory and remote host:

The shell buffer name you give to the prompt for a universal arg
can include an appended path. That will be used for the startup
directory. You can use tramp remote syntax to specify a remote
shell. If there is an element after a final '/', that's used for
the buffer name. Otherwise, the host, domain, or path is used.

For example:

* '#root/sudo:root@localhost:/etc' for a buffer named \"*#root*\" with a
  root shell starting in /etc.

* '/ssh:example.net:' for a shell buffer in your homedir on example.net. 
  The buffer will be named \"*example.net*\".

* '#ex/ssh:example.net|sudo:root@example.net:/var/log' for a root shell
  starting in /var/log on example.net named \"*#ex*\".

* 'interior/ssh:gateway.corp.com|ssh:interior.corp.com:' to go
  via gateway.corp.com to your homedir on interior.corp.com.  The
  buffer will be named \"*interior*\". You could append a sudo
  hop to the path, combining the previous example, and so on.

File visits from the shell, and many common emacs activities like
dired, will be on the host where the shell is running, in the
auspices of the target account, and relative to the current
directory.

You can change the startup path for a shell buffer by editing it
at the completion prompt. The new path will not take effect for
an already-running shell.

To remove a shell buffer's history entry, kill the buffer and
affirm removal of the entry when prompted.

===== Activate savehist to retain shell buffer names and paths across Emacs restarts:

To have emacs maintain your history of shell buffer names and paths,
customize the savehist group to activate savehist."

  (interactive "P")

  (let ((token '(token)))
    (if (window-minibuffer-p)
        (throw 'multishell-do-list token)
      (if (equal token
                 (catch 'multishell-do-list
                   (multishell-pop-to-shell-worker arg name here)))
          (multishell-list)))))

(defun multishell-pop-to-shell-worker (&optional arg name here)
  "Do real work of `multishell-pop-to-shell', which see."
  (let* ((from-buffer (current-buffer))
         (from-buffer-is-shell (derived-mode-p 'shell-mode))
         (primary-name-unbracketed (multishell-unbracket
                                    multishell-primary-name))
         (fallthrough-name (if from-buffer-is-shell
                               (buffer-name from-buffer)
                             primary-name-unbracketed))
         (doublearg (equal arg '(16)))
         (target-name-and-path
          (multishell-resolve-target-name-and-path
           (cond (name name)
                 (arg
                  (or (multishell-read-unbracketed-entry
                       (format "Shell buffer name [%s]%s "
                               primary-name-unbracketed
                               (if doublearg " <==" ":"))
                       primary-name-unbracketed)
                      primary-name-unbracketed))
                 (t fallthrough-name))))
         (use-path (cadr target-name-and-path))
         (target-shell-buffer-name (car target-name-and-path))
         (target-buffer (get-buffer target-shell-buffer-name))
         (curr-buff-proc (get-buffer-process from-buffer))
         inwin
         already-there)

    ;; Register early so the entry is pushed to the front:
    (multishell-register-name-to-path (multishell-unbracket
                                       target-shell-buffer-name)
                                      use-path)

    (when doublearg
      (setq multishell-primary-name target-shell-buffer-name))

    ;; Situate:

    (cond 

     ((and (or curr-buff-proc from-buffer-is-shell)
           (not arg)
           (eq from-buffer target-buffer)
           (not (eq target-shell-buffer-name (buffer-name from-buffer))))
      ;; In a shell buffer, but not named - stay in buffer, but go to end.
      (setq already-there t))

     ((string= (buffer-name) target-shell-buffer-name)
      ;; Already in the specified shell buffer:
      (setq already-there t))

     ((or (not target-buffer)
          (not (setq inwin
                     (multishell-get-visible-window-for-buffer target-buffer))))
      ;; No preexisting shell buffer, or not in a visible window:
      (when (not (get-buffer target-shell-buffer-name))
        (message "Creating new shell buffer '%s'" target-shell-buffer-name))
      (if here
          (switch-to-buffer target-shell-buffer-name)
        (pop-to-buffer target-shell-buffer-name pop-up-windows)))

     ;; Buffer exists and already has a window - jump to it:
     (t (if (and multishell-pop-to-frame
                 inwin
                 (not (equal (window-frame (selected-window))
                             (window-frame inwin))))
            (select-frame-set-input-focus (window-frame inwin)))
        (if (not (string= (buffer-name (current-buffer))
                          target-shell-buffer-name))
            (if here
                (switch-to-buffer target-shell-buffer-name)
              (pop-to-buffer target-shell-buffer-name t)))))

    ;; We're in the buffer. Activate:

    (if (not (comint-check-proc (current-buffer)))
        (multishell-start-shell-in-buffer (buffer-name (current-buffer))
                                          use-path))

    ;; If the destination buffer has a stopped process, resume it:
    (let ((process (get-buffer-process (current-buffer))))
      (if (and process (equal 'stop (process-status process)))
          (continue-process process)))

    (when (or already-there
             (equal (current-buffer) from-buffer))
      (goto-char (point-max))
      (and (get-buffer-process from-buffer)
           (goto-char (process-mark (get-buffer-process from-buffer)))))))

(defun multishell-delete-history-name (name &optional ask)
  "Remove all multishell history entries for NAME.

if optional ask is non-nil (default nil), ask before each deletion.

Return the last entry deleted."
  (let (got)
    (dolist (entry (multishell-history-entries name) got)
      (when (and entry
                 (or (not ask)
                     (y-or-n-p (format "Remove multishell history entry `%s'? "
                                       entry))))
        (setq got entry
              multishell-history (delete entry multishell-history))))))

(defun multishell-kill-buffer-query-function ()
  "Offer to remove multishell-history entry for buffer."
  ;; Removal choice is crucial, so users can, eg, kill a shell with huge
  ;; output backlog, while keeping the history entry to easily restart it.
  ;;
  ;; We use kill-buffer-query-functions instead of kill-buffer-hook because:
  ;;
  ;; 1. It enables the user to remove the history without actually killing a
  ;;    running buffer, by not confirming the subsequent running-proc query.
  ;; 2. kill-buffer-hooks often fails to run when killing shell buffers!
  ;;    It's probably due to failures in other hooks - beyond our control -
  ;;    and anyway, I like the first reason well enough.

  ;; (Use condition-case to avoid inadvertant disruption of kill-buffer
  ;; activity.  kill-buffer happens behind the scenes a whole lot.)
  (condition-case err
      (and (derived-mode-p 'shell-mode)
           (multishell-delete-history-name
            (multishell-unbracket (buffer-name))
            t))
    (error
     (message "multishell-kill-buffer-query-function error: %s" err)))
  t)
(add-hook 'kill-buffer-query-functions 'multishell-kill-buffer-query-function)

(defun multishell-get-visible-window-for-buffer (buffer)
  "Return visible window containing buffer."
  (catch 'got-a-vis
    (walk-windows
     (function (lambda (win)
                 (if (and (eq (window-buffer win) buffer)
                          (equal (frame-parameter
                                  (selected-frame) 'display)
                                 (frame-parameter
                                  (window-frame win) 'display)))
                     (throw 'got-a-vis win))))
     nil 'visible)
    nil))

(defun multishell-all-entries (&optional active-duplicated)
  "Return multishell history, with active buffers listed first.

Optional ACTIVE-DUPLICATED will return a copy of
`multishell-history' with unbracketed names of active buffers,
sans paths, appended to the list, so they have short and long
completions."
  ;; Reorder so active lead present lead historical entries:
  (let (active-entries active-names present past splat name path buffer)
    (dolist (entry multishell-history)
      (setq splat (multishell-split-entry entry)
            name (car splat)
            path (cadr splat)
            buffer (and name (get-buffer (multishell-bracket name))))
      (if (buffer-live-p buffer)
          (if (comint-check-proc buffer)
              (setq active-entries (push entry active-entries)
                    active-names (push name active-names))
            (setq present (push entry present)))
        (setq past (push entry past))))
    (setq multishell-history (append active-entries present past))
    (if active-duplicated
        (append multishell-history active-names)
      multishell-history)))

(defun multishell-read-unbracketed-entry (prompt default &optional initial)
  "PROMPT for shell buffer name, sans asterisks. Indicate DEFAULT in prompt.

Optional INITIAL is preliminary value to be edited.

Input and completion can include associated path, if any.

Return what's provided, if anything, else nil."
  (let* ((candidates (multishell-all-entries 'active-duplicated))
         (got (completing-read prompt
                               ;; COLLECTION:
                               (reverse candidates)
                               ;; PREDICATE:
                               nil
                               ;; REQUIRE-MATCH:
                               'confirm
                               ;; INITIAL-INPUT
                               initial
                               ;; HIST:
                               'multishell-history)))
    (if (not (string= got ""))
        got
      nil)))

(defun multishell-resolve-target-name-and-path (path-ish)
  "Given name/tramp-path PATH-ISH, resolve buffer name and initial directory.

The name is the part of the string up to the first '/' slash, if
any. Missing pieces are filled in from remote path elements, if
any, and multishell history. Given a path and no name, either the
host-name, domain-name, final directory name, or local host name
is used.

Return them as a list (name path), with name asterisk-bracketed
and path nil if none resolved."
  (let* ((splat (multishell-split-entry (or path-ish "")))
         (path (cadr splat))
         (name (or (car splat) (multishell-name-from-entry path))))
    (when (not path)
      ;; Get path from history, if present.
      (mapcar #'(lambda (entry)
                  (when (or (not path) (string= path ""))
                    (setq path (cadr (multishell-split-entry entry)))))
              (multishell-history-entries
               (multishell-unbracket name))))
    (list (multishell-bracket name) path)))

(defun multishell-name-from-entry (entry)
  "Derive a name for a shell buffer according to ENTRY."
  (if (not entry)
      (multishell-unbracket multishell-primary-name)
    (let* ((splat (multishell-split-entry entry))
           (name (car splat))
           (path (cadr splat)))
      (or name
          (if (file-remote-p path)
              (let ((vec (tramp-dissect-file-name path)))
                (or (tramp-file-name-host vec)
                    (tramp-file-name-domain vec)
                    (tramp-file-name-localname vec)
                    system-name))
            (multishell-unbracket multishell-primary-name))))))

(defun multishell-start-shell-in-buffer (buffer-name path)
  "Start, restart, or continue a shell in BUFFER-NAME on PATH."
  (let* ((buffer (get-buffer buffer-name))
         is-active)

    (set-buffer buffer)
    (setq is-active (comint-check-proc buffer))

    (when (and path (not is-active))

      (when (and (derived-mode-p 'shell-mode) (file-remote-p path))
        ;; Returning to disconnected remote shell - do some tidying:
        (tramp-cleanup-connection
         (tramp-dissect-file-name default-directory 'noexpand)
         'keep-debug 'keep-password))

      (when (file-remote-p path) (message "Connecting to %s" path))
      (cd path))

    (shell buffer)))

(defun multishell-track-dirchange (name newpath)
  "Change multishell history entry to track current directory."
  (let* ((entries (multishell-history-entries name)))
    (dolist (entry entries)
      (let* ((name-path (multishell-split-entry entry))
             (name (car name-path))
             (path (or (cadr name-path) "")))
        (when path
          (let* ((is-remote (file-remote-p path))
                 (vec (and is-remote (tramp-dissect-file-name path nil)))
                 (localname (if is-remote
                                (tramp-file-name-localname vec)
                              path))
                 (newlocalname
                  (replace-regexp-in-string (if (string= localname "")
                                                "$"
                                              (regexp-quote localname))
                                            ;; REP
                                            newpath
                                            ;; STRING
                                            localname
                                            ;; FIXEDCASE
                                            t
                                            ;; LITERAL
                                            t
                                            ))
                 (newpath (if is-remote
                              (tramp-make-tramp-file-name (aref vec 0)
                                                          (aref vec 1)
                                                          (aref vec 2)
                                                          newlocalname
                                                          (aref vec 4))
                            newpath))
                 (newentry (concat name newpath))
                 (membership (member entry multishell-history)))
            (when membership
              (setcar membership newentry))))))))
(defvar multishell-was-default-directory ()
  "Provide for tracking directory changes.")
(make-variable-buffer-local 'multishell-was-default-directory)
(defun multishell-post-command-business ()
  "Do multishell bookkeeping."
  ;; Update multishell-history with dir changes.
  (condition-case err
      (when (and multishell-history-entry-tracks-current-directory
                 (derived-mode-p 'shell-mode))
        (let ((curdir (if (file-remote-p default-directory)
                          (tramp-file-name-localname
                           (tramp-dissect-file-name default-directory))
                        default-directory)))
          (when (not (string= curdir (or multishell-was-default-directory "")))
            (multishell-track-dirchange (multishell-unbracket (buffer-name))
                                        curdir))
          (setq multishell-was-default-directory curdir)))
    ;; To avoid disruption as a pervasive hook function, swallow all errors:
    (error
     (message "multishell-post-command-business error: %s" err))))
(add-hook 'post-command-hook 'multishell-post-command-business)

(defun multishell-split-entry (entry)
  "Given multishell name/path ENTRY, return the separated name and path pair.

Returns nil for empty parts, rather than the empty string."
  (save-match-data
    (string-match "^\\([^/]*\\)\\(/?.*\\)?" entry)
    (let ((name (match-string 1 entry))
          (path (match-string 2 entry)))
      (and (string= name "") (setq name nil))
      (and (string= path "") (setq path nil))
      (list name path))))
(defun multishell-bracket (name)
  "Return a copy of name, ensuring it has an asterisk at the beginning and end."
  (if (not (string= (substring name 0 1) "*"))
      (setq name (concat "*" name)))
  (if (not (string= (substring name -1) "*"))
      (setq name (concat name "*")))
  name)
(defun multishell-unbracket (name)
  "Return a copy of name, removing asterisks, if any, at beginning and end."
  (if (string= (substring name 0 1) "*")
      (setq name (substring name 1)))
  (if (string= (substring name -1) "*")
      (setq name (substring name 0 -1)))
  name)

(provide 'multishell)

;;; multishell.el ends here