dotemacs

with-editor.org (12226B)

---

 #+title: With-Editor User Manual
 :PREAMBLE:
 #+author: Jonas Bernoulli
 #+email: jonas@bernoul.li
 #+date: 2015-{{{year}}}
 
 #+texinfo_dir_category: Emacs
 #+texinfo_dir_title: With-Editor: (with-editor).
 #+texinfo_dir_desc: Using the Emacsclient as $EDITOR
 #+subtitle: for version 3.3.2
 
 #+setupfile: .orgconfig
 
 The library ~with-editor~ makes it easy to use the Emacsclient as the
 ~$EDITOR~ of child processes, making sure they know how to call home.
 For remote processes a substitute is provided, which communicates with
 Emacs on standard output instead of using a socket as the Emacsclient
 does.
 
 This library was written because Magit has to be able to do the above
 to allow the user to edit commit messages gracefully and to edit
 rebase sequences, which wouldn't be possible at all otherwise.
 
 Because other packages can benefit from such functionality, this
 library is made available as a separate package.  It also defines some
 additional functionality which makes it useful even for end-users, who
 don't use Magit or another package which uses it internally.
 
 #+texinfo: @noindent
 This manual is for With-Editor version 3.3.2.
 
 #+texinfo: @insertcopying
 :END:
 * Using the With-Editor package
 
 The ~With-Editor~ package is used internally by Magit when editing
 commit messages and rebase sequences.  It also provides some commands
 and features which are useful by themselves, even if you don't use
 Magit.
 
 For information about using this library in you own package, see
 [[*Using With-Editor as a library]].
 
 ** Configuring With-Editor
 
 With-Editor tries very hard to locate a suitable ~emacsclient~
 executable, so ideally you should never have to customize the option
 ~with-editor-emacsclient-executable~.  When it fails to do so, then the
 most likely reason is that someone found yet another way to package
 Emacs (most likely on macOS) without putting the executable on ~$PATH~,
 and we have to add another kludge to find it anyway.
 
 - User Option: with-editor-emacsclient-executable ::
 
   The ~emacsclient~ executable used as the editor by child process of
   this Emacs instance.  By using this executable, child processes can
   call home to their parent process.
 
   This option is automatically set at startup by looking in ~exec-path~,
   and other places where the executable could be installed, to find
   the ~emacsclient~ executable most suitable for the current Emacs
   instance.
 
   You should *not* customize this option permanently.  If you have to do
   it, then you should consider that a temporary kludge and inform the
   Magit maintainer as described in [[*Debugging][Debugging]].
 
   If With-Editor fails to find a suitable ~emacsclient~ on you system,
   then this should be fixed for all users at once, by teaching
   ~with-editor-locate-emacsclient~ how to do so on your system and
   system like yours. Doing it this way has the advantage, that you
   won't have do it again every time you update Emacs, and that other
   users who have installed Emacs the same way as you have, won't have
   to go through the same trouble.
 
   Note that there also is a nuclear option; setting this variable to
   ~nil~ causes the "sleeping editor" described below to be used even for
   local child processes.  Obviously we don't recommend that you use
   this except in "emergencies", i.e., before we had a change to add a
   kludge appropriate for you setup.
 
 - Function: with-editor-locate-emacsclient ::
 
   The function used to set the initial value of the option
   ~with-editor-emacsclient-executable~.  There's a lot of voodoo here.
 
 The ~emacsclient~ cannot be used when using Tramp to run a process on a
 remote machine.  (Theoretically it could, but that would be hard to
 setup, very fragile, and rather insecure).
 
 With-Editor provides an alternative "editor" which can be used by
 remote processes in much the same way as local processes use an
 ~emacsclient~ executable.  This alternative is known as the "sleeping
 editor" because it is implemented as a shell script which sleeps until
 it receives a signal.
 
 - User Option: with-editor-sleeping-editor ::
 
   The sleeping editor is a shell script used as the editor of child
   processes when the ~emacsclient~ executable cannot be used.
 
   This fallback is used for asynchronous process started inside the
   macro ~with-editor~, when the process runs on a remote machine or for
   local processes when ~with-editor-emacsclient-executable~ is ~nil~.
 
   Where the latter uses a socket to communicate with Emacs' server,
   this substitute prints edit requests to its standard output on
   which a process filter listens for such requests.  As such it is
   not a complete substitute for a proper ~emacsclient~, it can only
   be used as ~$EDITOR~ of child process of the current Emacs instance.
 
   Some shells do not execute traps immediately when waiting for a
   child process, but by default we do use such a blocking child
   process.
 
   If you use such a shell (e.g., ~csh~ on FreeBSD, but not Debian), then
   you have to edit this option.  You can either replace ~sh~ with ~bash~
   (and install that), or you can use the older, less performant
   implementation:
 
   #+BEGIN_SRC emacs-lisp
     "sh -c '\
     echo \"WITH-EDITOR: $$ OPEN $0$1 IN $(pwd)\"; \
     trap \"exit 0\" USR1; \
     trap \"exit 1\" USR2; \
     while true; do sleep 1; done'"
   #+END_SRC
 
   Note that the unit separator character () right after the file
   name ($0) is required.
 
   Also note that using this alternative implementation leads to a
   delay of up to a second.  The delay can be shortened by replacing
   ~sleep 1~ with ~sleep 0.01~, or if your implementation does not support
   floats, then by using ~nanosleep~ instead.
 
 ** Using With-Editor commands
 
 This section describes how to use the ~with-editor~ library /outside/ of
 Magit.  You don't need to know any of this just to create commits
 using Magit.
 
 The commands ~with-editor-async-shell-command~ and
 ~with-editor-shell-command~ are intended as drop in replacements for
 ~async-shell-command~ and ~shell-command~.  They automatically export
 ~$EDITOR~ making sure the executed command uses the current Emacs
 instance as "the editor".  With a prefix argument these commands
 prompt for an alternative environment variable such as ~$GIT_EDITOR~.
 
 - Command: with-editor-async-shell-command ::
 
   This command is like ~async-shell-command~, but it runs the shell
   command with the current Emacs instance exported as ~$EDITOR~.
 
 - Command: with-editor-shell-command ::
 
   This command is like ~shell-command~, but if the shell command ends
   with ~&~ and is therefore run asynchronously, then the current Emacs
   instance is exported as ~$EDITOR~.
 
 To always use these variants add this to you init file:
 
 #+begin_src emacs-lisp
   (define-key (current-global-map)
     [remap async-shell-command] 'with-editor-async-shell-command)
   (define-key (current-global-map)
     [remap shell-command] 'with-editor-shell-command)
 #+end_src
 
 Alternatively use the global ~shell-command-with-editor-mode~.
 
 - Variable: shell-command-with-editor-mode ::
 
   When this mode is active, then ~$EDITOR~ is exported whenever
   ultimately ~shell-command~ is called to asynchronously run some shell
   command.  This affects most variants of that command, whether they
   are defined in Emacs or in some third-party package.
 
 The command ~with-editor-export-editor~ exports ~$EDITOR~ or another
 such environment variable in ~shell-mode~, ~eshell-mode~, ~term-mode~ and
 ~vterm-mode~ buffers.  Use this Emacs command before executing a shell
 command which needs the editor set, or always arrange for the current
 Emacs instance to be used as editor by adding it to the appropriate
 mode hooks:
 
 #+begin_src emacs-lisp
   (add-hook 'shell-mode-hook  'with-editor-export-editor)
   (add-hook 'eshell-mode-hook 'with-editor-export-editor)
   (add-hook 'term-exec-hook   'with-editor-export-editor)
   (add-hook 'vterm-mode-hook  'with-editor-export-editor)
 #+end_src
 
 Some variants of this function exist; these two forms are equivalent:
 
 #+begin_src emacs-lisp
   (add-hook 'shell-mode-hook
             (apply-partially 'with-editor-export-editor "GIT_EDITOR"))
   (add-hook 'shell-mode-hook 'with-editor-export-git-editor)
 #+end_src
 
 - Command: with-editor-export-editor ::
 
   When invoked in a ~shell-mode~, ~eshell-mode~, ~term-mode~ or ~vterm-mode~
   buffer, this command teaches shell commands to use the current Emacs
   instance as the editor, by exporting ~$EDITOR~.
 
 - Command: with-editor-export-git-editor ::
 
   This command is like ~with-editor-export-editor~ but exports
   ~$GIT_EDITOR~.
 
 - Command: with-editor-export-hg-editor ::
 
   This command is like ~with-editor-export-editor~ but exports
   ~$HG_EDITOR~.
 
 * Using With-Editor as a library
 
 This section describes how to use the ~with-editor~ library /outside/ of
 Magit to teach another package how to have its child processes call
 home, just like Magit does.  You don't need to know any of this just
 to create commits using Magit.  You can also ignore this if you use
 ~with-editor~ outside of Magit, but only as an end-user.
 
 For information about interactive use and options that affect both
 interactive and non-interactive use, see [[*Using the With-Editor
 package]].
 
 - Macro: with-editor &rest body ::
 
   This macro arranges for the ~emacsclient~ or the sleeping editor to be
   used as the editor of child processes, effectively teaching them to
   call home to the current Emacs instance when they require that the
   user edits a file.
 
   This is done by establishing a local binding for ~process-environment~
   and changing the value of the ~EDITOR~ environment variable in that
   scope.  This affects all (asynchronous) processes started by forms
   (dynamically) inside BODY.
 
   If BODY begins with a literal string, then that variable is set
   instead of ~EDITOR~.
 
 - Macro: with-editor envvar &rest body ::
 
   This macro is like ~with-editor~ instead that the ENVVAR argument is
   required and that it is evaluated at run-time.
 
 - Function: with-editor-set-process-filter process filter ::
 
   This function is like ~set-process-filter~ but ensures that adding the
   new FILTER does not remove the ~with-editor-process-filter~.  This is
   done by wrapping the two filter functions using a lambda, which
   becomes the actual filter.  It calls FILTER first, which may or
   may not insert the text into the PROCESS's buffer.  Then it calls
   ~with-editor-process-filter~, passing t as NO-STANDARD-FILTER.
 
 * Debugging
 
 With-Editor tries very hard to locate a suitable ~emacsclient~
 executable, and then sets option ~with-editor-emacsclient-executable~
 accordingly.  In very rare cases this fails.  When it does fail, then
 the most likely reason is that someone found yet another way to
 package Emacs (most likely on macOS) without putting the executable on
 ~$PATH~, and we have to add another kludge to find it anyway.
 
 If you are having problems using ~with-editor~, e.g., you cannot commit
 in Magit, then please open a new issue at
 https://github.com/magit/with-editor/issues and provide information
 about your Emacs installation.  Most importantly how did you install
 Emacs and what is the output of ~M-x with-editor-debug RET~.
 
 * Function and Command Index
 :PROPERTIES:
 :APPENDIX:   t
 :INDEX:      fn
 :END:
 * Variable Index
 :PROPERTIES:
 :APPENDIX:   t
 :INDEX:      vr
 :END:
 * Copying
 :PROPERTIES:
 :COPYING:    t
 :END:
 
 #+begin_quote
 Copyright (C) 2015-{{{year}}} Jonas Bernoulli <jonas@bernoul.li>
 
 You can redistribute this document 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.
 
 This document 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.
 #+end_quote
 
 # LocalWords: LocalWords
 # LocalWords: Magit Emacs emacsclient FreeBSD macOS texinfo
 # LocalWords: async eval hg init performant rebase startup
 
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