* Key rebinding::
* Smart scrolling::
* Terminal emulation::
+* Electric forward slash::
@end menu
@node Writing a module
This section is not yet written.
+@node Electric forward slash
+@section Electric forward slash
+
+To help with supplying absolute file name arguments to remote
+commands, you can add the @code{eshell-elecslash} module to
+@code{eshell-modules-list}. Then, typing @kbd{/} as the first
+character of a command line argument will automatically insert the
+Tramp prefix @file{/method:host:}. If this is not what you want
+(e.g.@: because you want to refer to a local file), you can type
+another @kbd{/} to undo the automatic insertion. Typing @kbd{~/} also
+inserts the Tramp prefix. The automatic insertion applies only when
+@code{default-directory} is remote and the command is a Lisp function.
+In particular, typing arguments to external commands doesn't insert
+the prefix.
+
+The result is that in most cases of supplying absolute file name
+arguments to commands you should see the Tramp prefix inserted
+automatically only when that's what you'd reasonably expect. This
+frees you from having to keep track of whether commands are Lisp
+functions or external when typing command line arguments. For
+example, suppose you execute
+
+@example
+ cd /ssh:root@@example.com:
+ find /etc -name "*gnu*"
+@end example
+
+@noindent and in reviewing the output of the command, you identify a
+file @file{/etc/gnugnu} that should be moved somewhere else. So you
+type
+
+@example
+ mv /etc/gnugnu /tmp
+@end example
+
+@noindent But since @command{mv} refers to the local Lisp function
+@code{eshell/mv}, not a remote shell command, to say this is to
+request that the local file @file{/etc/gnugnu} be moved into the local
+@file{/tmp} directory. After you add @code{eshell-elecslash} to
+@code{eshell-modules-list}, then when you type the above @command{mv}
+invocation you will get the following input, which is what you
+intended:
+
+@example
+ mv /ssh:root@@example.com:/etc/gnugnu /ssh:root@@example.com:/tmp
+@end example
+
+The code that determines whether or not the Tramp prefix should be
+inserted uses simple heuristics. A limitation of the current
+implementation is that it inspects whether only the command at the
+very beginning of input is a Lisp function or external program. Thus
+when chaining commands with the operators @code{&&}, @code{||},
+@code{|} and @code{;}, the electric forward slash is active only
+within the first command.
+
@node Bugs and ideas
@chapter Bugs and ideas
@cindex reporting bugs and ideas
@item The first keypress after @kbd{M-x watson} triggers
@code{eshell-send-input}
-@item Make @kbd{/} electric
+@item Make @kbd{/} more electric
-So that it automatically expands and corrects pathnames. Or make
-pathname completion for Pcomplete auto-expand @samp{/u/i/std@key{TAB}} to
-@samp{/usr/include/std@key{TAB}}.
+@noindent so that it automatically expands and corrects file names,
+beyond what the @code{em-elecslash} module is able to do. Or make
+file name completion for Pcomplete auto-expand
+@samp{/u/i/std@key{TAB}} to @samp{/usr/include/std@key{TAB}}.
@item Write the @command{pushd} stack to disk along with @code{last-dir-ring}
--- /dev/null
+;;; em-elecslash.el --- electric forward slashes -*- lexical-binding:t -*-
+
+;; Copyright (C) 2022 Free Software Foundation, Inc.
+
+;; Author: Sean Whitton <spwhitton@spwhitton.name>
+
+;; This file is part of GNU Emacs.
+
+;; GNU Emacs is free software: you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version.
+
+;; GNU Emacs is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with GNU Emacs. If not, see <https://www.gnu.org/licenses/>.
+
+;;; Commentary:
+
+;; Electric forward slash in remote Eshells.
+
+;;; Code:
+
+(require 'tramp)
+(require 'thingatpt)
+(require 'esh-cmd)
+(require 'esh-ext)
+(require 'esh-mode)
+
+;; This makes us an option when customizing `eshell-modules-list'.
+;;;###autoload
+(progn
+(defgroup eshell-elecslash nil
+ "Electric forward slash in remote Eshells.
+
+This module helps with supplying absolute file name arguments to
+remote commands. After enabling it, typing a forward slash as
+the first character of a command line argument will automatically
+insert the Tramp prefix, /method:host:. The automatic insertion
+applies only when `default-directory' is remote and the command
+is a Lisp function.
+
+The result is that in most cases of supplying absolute file name
+arguments to commands you should see the Tramp prefix inserted
+automatically only when that's what you'd reasonably expect.
+This frees you from having to keep track of whether commands are
+Lisp functions or external when typing command line arguments."
+ :tag "Electric forward slash"
+ :group 'eshell-module))
+
+;;; Functions:
+
+(defun eshell-elecslash-initialize () ;Called from `eshell-mode' via intern-soft!
+ "Initialize remote Eshell electric forward slash support."
+ (add-hook 'post-self-insert-hook
+ #'eshell-electric-forward-slash nil t))
+
+(defun eshell-electric-forward-slash ()
+ "Implementation of electric forward slash in remote Eshells.
+
+Initializing the `eshell-elecslash' module adds this function to
+`post-self-insert-hook'. Typing / or ~/ as the first character
+of a command line argument automatically inserts the Tramp prefix
+in the case that `default-directory' is remote and the command is
+a Lisp function. Typing a second forward slash undoes the
+insertion."
+ (when (eq ?/ (char-before))
+ (delete-char -1)
+ (let ((tilde-before (eq ?~ (char-before)))
+ (command (save-excursion
+ (eshell-bol)
+ (skip-syntax-forward " ")
+ (thing-at-point 'sexp))))
+ (if (and (file-remote-p default-directory)
+ ;; We can't formally parse the input. But if there is
+ ;; one of these operators behind us, then looking at
+ ;; the first command would not be sensible. So be
+ ;; conservative: don't insert the Tramp prefix if there
+ ;; are any of these operators behind us.
+ (not (looking-back (regexp-opt '("&&" "|" ";"))
+ eshell-last-output-end))
+ (or (= (point) eshell-last-output-end)
+ (and tilde-before
+ (= (1- (point)) eshell-last-output-end))
+ (and (or tilde-before
+ (eq ?\s (char-syntax (char-before))))
+ (or (eshell-find-alias-function command)
+ (and (fboundp (intern-soft command))
+ (or eshell-prefer-lisp-functions
+ (not (eshell-search-path command))))))))
+ (let ((map (make-sparse-keymap))
+ (start (if tilde-before (1- (point)) (point)))
+ (localname
+ (tramp-file-name-localname
+ (tramp-dissect-file-name default-directory))))
+ (when tilde-before (delete-char -1))
+ (insert
+ (substring default-directory 0
+ (string-search localname default-directory)))
+ (unless tilde-before (insert "/"))
+ ;; Typing a second slash undoes the insertion, for when
+ ;; you really do want to type a local absolute file name.
+ (define-key map "/" (lambda ()
+ (interactive)
+ (delete-region start (point))
+ (insert (if tilde-before "~/" "/"))))
+ (set-transient-map map))
+ (insert "/")))))
+
+(provide 'em-elecslash)
+
+;; Local Variables:
+;; generated-autoload-file: "esh-groups.el"
+;; End:
+
+;;; esh-elecslash.el ends here
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