= image:{logo}[K,30,30,link="{website}"] Kakoune image:{travis-img}[link="{travis-url}"]
:logo: https://rawgit.com/mawww/kakoune/master/doc/kakoune_logo.svg
:website: http://kakoune.org
:travis-img: https://travis-ci.org/mawww/kakoune.svg?branch=master
:travis-url: https://travis-ci.org/mawww/kakoune
:icons: font
:toc: right

TL;DR
-----

{website}

*Vim inspired* -- *Faster as in less keystrokes* --
*Multiple selections* -- *Orthogonal design*

---------------------------------------------
git clone http://github.com/mawww/kakoune.git
cd kakoune/src
make
./kak
---------------------------------------------

See http://github.com/mawww/golf for kakoune solutions to vimgolf challenges,
regularly beating the best vim solution.

See the link:doc/design.asciidoc[design document] for more information on
Kakoune philosophy and design.

:numbered:

Introduction
------------

Kakoune is a code editor heavily inspired by Vim, as such most of its
commands are similar to vi's ones, and it shares Vi's "keystrokes as
a text editing language" model.

Kakoune can operate in two modes, normal and insertion. In insertion mode,
keys are directly inserted into the current buffer. In normal mode, keys
are used to manipulate the current selection and to enter insertion mode.

Kakoune has a strong focus on interactivity, most commands provide immediate
and incremental results, while still being competitive (as in keystroke count)
with Vim.

Kakoune works on selections, which are oriented, inclusive range of characters,
selections have an anchor and a cursor character. Most commands move both of
them, except when extending selection where the anchor character stays fixed
and the cursor one moves around.

see http://vimeo.com/82711574

Join us on freenode IRC `#Kakoune`

Features
~~~~~~~~

 * Multiple selections as a central way of interacting
 * Powerful selection manipulation primitives
   - Select all regex matches in current selections
   - Keep selections containing/not containing a match for a given regex
   - Split current selections with a regex
   - Text objects (paragraph, sentence, nestable blocks)
 * Powerful text manipulation primitives
   - Align selections
   - Rotate selection contents
   - Case manipulation
   - Indentation
   - Piping each selection to external filter
 * Client-Server architecture
   - Multiple clients on the same editing session
   - Use tmux or your X11 window manager to manage windows
 * Simple interaction with external programs
 * Automatic contextual help
 * Automatic as you type completion
 * Macros
 * Hooks
 * Syntax Highlighting
   - Supports multiple languages in the same buffer
   - Highlight a buffer differently in different windows

Screenshots
~~~~~~~~~~~

[[screenshot-i3]]
.Kakoune in i3
image::doc/screenshot-i3.gif[Kakoune in i3]

[[screenshot-tmux]]
.Kakoune in tmux
image::doc/screenshot-tmux.gif[Kakoune in tmux]

Getting started
---------------

Building
~~~~~~~~

Kakoune dependencies are:

 * A C\+\+11 compliant compiler (GCC >= 5 or clang >= 3.4) along with its
   associated C\+\+ standard library (libstdc\+\+ or libc\+\+)
 * boost (>= 1.50)
 * ncurses with wide-characters support (>= 5.3, generally referred to as libncursesw)
 * asciidoc (for the `a2k` tool), to generate man pages

To build, just type *make* in the src directory.
To generate man pages, type *make doc* in the src directory.

Kakoune can be built on Linux, MacOS, and Cygwin. Due to Kakoune relying heavily
on being in a Unix-like environment, no native Windows version is planned.

Installing
~~~~~~~~~~

In order to install kak on your system, rather than running it directly from
its source directory, type *make install*, you can specify the `PREFIX` and
`DESTDIR` if needed.

[TIP]
.Homebrew (OSX)
====
NOTE: The ncurses library that comes with OSX is not new enough to support some
of the mouse based features of Kakoune (only tested on OSX 10.11.3, where the
packaged ncurses library is version 5.4, whereas the latest version is 6.0).
Currently, a fresh Kakoune install requires that you install ncurses 6.0. You
can install ncurses 6.0 via Homebrew,
-----------------------------------
brew install homebrew/dupes/ncurses
-----------------------------------

Then, to install,
---------------------------------------------------------------------------------------------
brew install --HEAD https://raw.githubusercontent.com/mawww/kakoune/master/contrib/kakoune.rb
---------------------------------------------------------------------------------------------

To update kakoune,
---------------------------------
brew upgrade --fetch-HEAD kakoune
---------------------------------
====

[TIP]
.Fedora 22/23/24/Rawhide
====
Use the https://copr.fedoraproject.org/coprs/jkonecny/kakoune/[copr]
repository.

---------------------------------
dnf copr enable jkonecny/kakoune
dnf install kakoune
---------------------------------
====

[TIP]
.Arch Linux
====
A PKGBUILD https://aur.archlinux.org/packages/kakoune-git[kakoune-git]
to install Kakoune is available in the
https://wiki.archlinux.org/index.php/Arch_User_Repository[AUR].

--------------------------------------------------
# For example build and install Kakoune via yaourt
yaourt -Sy kakoune-git
--------------------------------------------------
====

[TIP]
.Gentoo
====
Kakoune is found in portage as
https://packages.gentoo.org/packages/app-editors/kakoune[app-editors/kakoune]
====

[TIP]
.Exherbo
====
--------------------------------
cave resolve -x repository/mawww
cave resolve -x kakoune
--------------------------------
====

[TIP]
.openSUSE
====
kakoune can be found in the
https://build.opensuse.org/package/show/editors/kakoune[editors] devel
project.  Make sure to adjust the link below to point to the repository of
your openSUSE version.

---------------------------------------------------------------------------------------------------
#Example for Tumbleweed:
sudo zypper addrepo http://download.opensuse.org/repositories/editors/openSUSE_Factory/editors.repo
sudo zypper refresh
sudo zypper install kakoune
---------------------------------------------------------------------------------------------------
====

[TIP]
.Debian
====
There is a script in
https://github.com/mawww/kakoune/blob/master/contrib/make_deb.bash[contrib/make_deb.bash]
that can be used to generate a debian package for kakoune.  You can then
install the generated .deb package with the dpkg tool.

--------------------------------------------------
./make_deb.bash -e "your_email" -f "your_username"
sudo dpkg -i thePackageName.deb
--------------------------------------------------

====

Running
~~~~~~~

Just running *kak* launch a new kak session with a client on local terminal.
*kak* accepts some switches:

 * `-c <session>`: connect to given session, sessions are unix sockets
       `/tmp/kak-<session>`
 * `-e <commands>`: execute commands on startup
 * `-n`: ignore kakrc file
 * `-s <session>`: set the session name, by default it will be the pid
       of the initial kak process.
 * `-d`: run Kakoune in daemon mode, without user interface. This requires
       the session name to be specified with -s. In this mode, the Kakoune
       server will keep running even if there is no connected client, and
       will quit when receiving SIGTERM.
 * `-p <session>`: read stdin, and then send its content to the given session
       acting as a remote control.
 * `-f <keys>`: Work as a filter, read every file given on the command line
       and stdin if piped in, and apply given keys on each.
 * `-ui <userinterface>`: use given user interface, `<userinterface>` can be
    - `ncurses`: default terminal user interface
    - `dummy`: empty user interface not displaying anything
    - `json`: json-rpc based user interface that writes json on stdout and
        read keystrokes as json on stdin.
 * `-l`: list existing sessions, and check the dead ones
 * `-clear`: clear dead sessions socket files
 * `-ro`: prevent modifications to all buffers from being saved to disk

At startup, if `-n` is not specified, Kakoune will try to source the file
`../share/kak/kakrc` relative to the kak binary. This kak file will then try
to recursively source any files in `$XDG_CONFIG_HOME/kak/autoload` (with
`$XDG_CONFIG_HOME` defaulting to `$HOME/.config`, and falling back to
`../share/kak/autoload/` if that autoload directory does not exists), then
`../share/kak/kakrc.local` if it exists, and finally `$XDG_CONFIG_HOME/kak/kakrc`.

That leads to the following behaviour: by default, with no user autoload
directory, the system wide autoload directory is used, once the user wants
control on autoloading, they can create an autoload directory and eventually
symlink individual scripts, or the whole system wide autoload directory. They
can as well add any new scripts not provided with Kakoune.

Basic Interaction
-----------------

Selections
~~~~~~~~~~

The main concept in Kakoune is the selection. A selection is an inclusive,
directed range of character. A selection has two ends, the anchor and the
cursor.

There is always at least one selection, and a selection is always at least
one character (in which case the anchor and cursor of the selections are
on the same character).

Normal Mode
~~~~~~~~~~~

In normal mode, keys are not inserted directly inside the buffer, but are editing
commands. These commands provides ways to manipulate either the selections themselves,
or the selected text.

Insert Mode
~~~~~~~~~~~

When entering insert mode, keys are now directly inserted before each selections
cursor. Some additional keys are recognised in insert mode:

 * `<esc>`: leave insert mode
 * `<backspace>`: delete characters before cursors
 * `<del>`: delete characters under cursors
 * `<left>, <right>, <up>, <down>`: move the cursors in given direction
 * `<home>`: move cursors to line begin
 * `<end>`: move cursors to end of line

 * `<c-n>`: select next completion candidate
 * `<c-p>`: select previous completion candidate
 * `<c-x>`: explicit insert completion query, followed by:
   - `f`: explicit file completion
   - `w`: explicit word completion
   - `l`: explicit line completion
 * `<c-o>`: disable automatic completion for this insert session

 * `<c-r>`: insert contents of the register given by next key
 * `<c-v>`: insert next keystroke directly into the buffer,
    without interpreting it.

 * `<c-u>`: commit changes up to now as a single undo group.

 * `<a-;>`: escape to normal mode for a single command

Movement
~~~~~~~~

 * `h`: select the character on the left of selection end
 * `j`: select the character below the selection end
 * `k`: select the character above the selection end
 * `l`: select the character on the right of selection end

 * `w`: select the word and following whitespaces  on the right of selection end
 * `b`: select preceding whitespaces and the word on the left of selection end
 * `e`: select preceding whitespaces and the word on the right of selection end
 * `alt-[wbe]`: same as [wbe] but select WORD instead of word

 * `f`: select to the next occurence of given character
 * `t`: select until the next occurence of given character
 * `<alt-[ft]>`: same as [ft] but in the other direction

 * `m`: select to matching character
 * `M`: extend selection to matching character

 * `x`: select line on which selection end lies (or next line when end lies on
        an end-of-line)
 * `alt-x`: expand selections to contain full lines (including end-of-lines)
 * `alt-X`: trim selections to only contain full lines (not including last
            end-of-line)

 * `%`: select whole buffer

 * `alt-h`: select to line begin
 * `alt-l`: select to line end

 * `/`: search (select next match)
 * `alt-/`: search (select previous match)
 * `?`: search (extend to next match)
 * `alt-?`: search (extend to previous match)
 * `n`: select next match
 * `N`: add a new selection with next match
 * `alt-n`: select previous match
 * `alt-N`: add a new selection with previous match

 * `pageup`: scroll up
 * `pagedown`: scroll down

 * `'`: rotate selections (the main selection becomes the next one)

 * `;`: reduce selections to their cursor
 * `alt-;`: flip the selections direction
 * `alt-:`: ensure selections are in forward direction (cursor after anchor)

 * `alt-.`: repeat last object or `f`/`t` selection command.


A word is a sequence of alphanumeric characters or underscore, a WORD is a
sequence of non whitespace characters.

Appending
~~~~~~~~~

for most selection commands, using shift permits to extend current selection
instead of replacing it. for example, `wWW` selects 3 consecutive words

Using Counts
~~~~~~~~~~~~

Most selection commands also support counts, which are entered before the
command itself.

for example, `3W` selects 3 consecutive words and `3w` select the third word on
the right of selection end.

Changes
~~~~~~~

 * `i`: enter insert mode before current selection
 * `a`: enter insert mode after current selection
 * `d`: yank and delete current selection
 * `c`: yank and delete current selection and enter insert mode
 * `.`: repeat last insert mode change (`i`, `a`, or `c`, including
        the inserted text)

 * `I`: enter insert mode at current selection begin line start
 * `A`: enter insert mode at current selection end line end
 * `o`: enter insert mode in one (or given count) new lines below
        current selection end
 * `O`: enter insert mode in one (or given count)  new lines above
        current selection begin

 * `y`: yank selections
 * `p`: paste after current selection end
 * `P`: paste before current selection begin
 * `alt-p`: paste all after current selection end, and
            select each pasted string.
 * `alt-P`: paste all before current selection begin, and
            select each pasted string.
 * `R`: replace current selection with yanked text

 * `r`: replace each character with the next entered one

 * `alt-j`: join selected lines
 * `alt-J`: join selected lines and select spaces inserted
            in place of line breaks
 * `alt-m`: merge contiguous selections together (works across lines as well)

 * `>`: indent selected lines
 * `alt->`: indent selected lines, including empty lines
 * `<`: deindent selected lines
 * `alt-<`: deindent selected lines, do not remove incomplete
        indent (3 leading spaces when indent is 4)

 * `|`: pipe each selections through the given external filter program
        and replace the selection with it's output.
 * `alt-|`: pipe each selections through the given external filter program
        and ignore its output

 * `!`: insert command output before selection
 * `a-!`: append command output after selection

 * `u`: undo last change
 * `a-u`: move backward in history
 * `U`: redo last change
 * `a-U`: move forward in history

 * `&`: align selection, align the cursor of selections by inserting
        spaces before the first character of the selection
 * `alt-&`: copy indent, copy the indentation of the main selection
        (or the count one if a count is given) to all other ones

 * ```: to lower case
 * `~`: to upper case
 * `alt-``: swap case

 * `@`: convert tabs to spaces in current selections, uses the buffer
        tabstop option or the count parameter for tabstop.
 * `alt-@`: convert spaces to tabs in current selections, uses the buffer
            tabstop option or the count parameter for tabstop.

 * `alt-'`: rotate selections content, if specified, the count groups
            selections, so `3<a-'>` rotate (1, 2, 3) and (3, 4, 6)
            independently.

Goto Commands
~~~~~~~~~~~~~

Commands beginning with g are used to goto certain position and or buffer:

 * `gh`: select to line begin
 * `gl`: select to line end

 * `gg`, `gk`: go to the first line
 * `gj`: go to the last line
 * `ge`: go to last char of last line

 * `gt`: go to the first displayed line
 * `gc`: go to the middle displayed line
 * `gb`: go to the last displayed line

 * `ga`: go to the previous (alternate) buffer
 * `gf`: open the file whose name is selected

 * `g.`: go to last buffer modification position

If a count is given prior to hitting `g`, `g` will jump to the given line.
Using `G` will extend the selection rather than jump.

View commands
~~~~~~~~~~~~~

Some commands, all beginning with v permit to manipulate the current
view.

 * `vv` or `vc`: center the main selection in the window
 * `vt`: scroll to put the main selection on the top line of the window
 * `vb`: scroll to put the main selection on the bottom line of the window
 * `vh`: scroll the window count columns left
 * `vj`: scroll the window count line downward
 * `vk`: scroll the window count line upward
 * `vl`: scroll the window count columns right

Using `V` will lock view mode until `<esc>` is hit

Marks
~~~~~

Current selections position can be saved in a register and restored later on.
By default, marks use the '^' register, but using the register can be set
using `"<reg>` prefix.

`Z` will save the current selections to the register.
`alt-Z` will append the current selections to the register.
`z` will restore the selections from the register.
`alt-z` will add the selections from the register to the existing ones.

Jump list
~~~~~~~~~

Some commands, like the goto commands, buffer switch or search commands,
push the previous selections to the client's jump list. It is possible
to forward or backward in the jump list using:

 * `control-i`: Jump forward
 * `control-o`: Jump backward
 * `control-s`: save current selections

Multi Selection
~~~~~~~~~~~~~~~

Kak was designed from the start to handle multiple selections.
One way to get a multiselection is via the `s` key.

For example, to change all occurrences of word 'roger' to word 'marcel'
in a paragraph, here is what can be done:

select the paragraph with enough `x`. press `s` and enter roger, then enter.
Now paragraph selection was replaced with multiselection of each roger in
the paragraph. Press `c` and marcel<esc> to replace rogers with marcels.

A multiselection can also be obtained with `S`, which splits the current
selection according to the regex entered. To split a comma separated list,
use `S` then ', *'

The regex syntax supported by Kakoune is the Perl one and is describe  
here <<Regex syntax>>.

`s` and `S` share the search pattern with `/`, and hence entering an empty
pattern uses the last one.

As a convenience, `alt-s` allows you to split the current selections on
line boundaries.

To clear multiple selections, use `space`. To keep only the nth selection
use `n` followed by `space`, in order to remove a selection, use `alt-space`.

`alt-k` allows you to enter a regex and keep only the selections that
contains a match for this regex. using `alt-K` you can keep the selections
not containing a match.

`C` copies the current selection to the next line (or lines if a count is given)
`alt-C` does the same to previous lines.

`$` allows you to enter a shell command and pipe each selections to it.
Selections whose shell command returns 0 will be kept, other will be dropped.

Object Selection
~~~~~~~~~~~~~~~~

Some keys allow you to select a text object:

 * `alt-a`: selects the whole object
 * `alt-i`: selects the inner object, that is the object excluding it's surrounder.
            for example, for a quoted string, this will not select the quote, and
            for a word this will not select trailing spaces.
 * `[`: selects to object start
 * `]`: selects to object end
 * `{`: extends selections to object start
 * `}`: extends selections to object end

After this key, you need to enter a second key in order to specify which
object you want.

 * `b`, `(` or `)`: select the enclosing parenthesis
 * `B`, `{` or `}`: select the enclosing {} block
 * `r`, `[` or `]`: select the enclosing [] block
 * `a`, `<` or `>`: select the enclosing <> block
 * `"` or `Q`: select the enclosing double quoted string
 * `'` or `q`: select the enclosing single quoted string
 * ``` or `g`: select the enclosing grave quoted string
 * `w`: select the whole word
 * `W`: select the whole WORD
 * `s`: select the sentence
 * `p`: select the paragraph
 * `␣`: select the whitespaces
 * `i`: select the current indentation block
 * `n`: select the number
 * `u`: select the argument
 * `:`: select user defined object, will prompt
   for open and close text.

For nestable objects, a count can be used in order to specify which surrounding
level to select.

Commands
--------

When pressing `:` in normal mode, Kakoune will open a prompt to enter a command.

Commands are used for non editing tasks, such as opening a buffer, writing the
current one, quitting, etc.

A few keys are recognized by prompt mode to help editing a command:

 * `<ret>`: validate prompt
 * `<esc>`: abandon without

 * `<left> or <a-h>`: move cursor to previous character
 * `<right> or <a-l>`: move cursor to previous character
 * `<home>`: move cursor to first character
 * `<end>`: move cursor to passed last character
 * `<backspace> or <a-x>`: erase character before cursor
 * `<del> or <a-d>`: erase character under cursor

 * `<c-w>`: advance to next word begin
 * `<c-a-w>`: advance to next WORD begin
 * `<c-b>`: go back to previous word begin
 * `<c-a-b>`: go back to previous WORD begin
 * `<c-e>`: advance to next word end
 * `<c-a-e>`: advance to next word end

 * `<up> or <c-p>`: select previous entry in history
 * `<down> or <c-n>`: select next entry in history

 * `<tab>`: select next completion candidate
 * `<backtab>`: select previous completion candidate

 * `<c-r>`: insert then content of the register given by next key.
 * `<c-v>`: insert next keystroke without interpreting it

 * `<c-o>`: disable auto completion for this prompt


Commands starting with horizontal whitespace (e.g. a space) will not be
saved in the command history.

Basic Commands
~~~~~~~~~~~~~~

Some commands take an exclamation mark (`!`), which can be used to force
the execution of the command (i.e. to quit a modified buffer, the
command `q!` has to be used).

 * `cd [<directory>]`: change the current directory to `<directory>`, or the home directory is unspecified
 * `doc <topic>`: display documentation about a topic. The completion list
     displays the available topics.
 * `e[dit][!] <filename> [<line> [<column>]]`: open buffer on file, go to given
     line and column. If file is already opened, just switch to this file.
     use edit! to force reloading.
 * `w[rite] [<filename>]`: write buffer to <filename> or use it's name if
     filename is not given.
 * `w[rite]a[ll]`: write all buffers that are associated to a file.
 * `q[uit][!]`: exit Kakoune, use quit! to force quitting even if there is some
     unsaved buffers remaining.
 * `kill[!]`: terminate the current session, all the clients as well as the server,
     use kill! to ignore unsaved buffers
 * `w[a]q[!]`: write the current buffer (or all buffers when `waq` is used) and quit
 * `b[uffer] <name>`: switch to buffer <name>
 * `b[uffer]n[ext]`: switch to the next buffer
 * `b[uffer]p[rev]`: switch to the previous buffer
 * `d[el]b[uf][!] [<name>]`: delete the buffer <name>
 * `source <filename>`: execute commands in <filename>
 * `runtime <filename>`: execute commands in <filename>, <filename>
     is relative to kak executable path.
 * `colorscheme <name>`: load named colorscheme.
 * `rename-client <name>`: set current client name
 * `rename-buffer <name>`: set current buffer name
 * `rename-session <name>`: set current session name
 * `echo [options] <text>`: show <text> in status line, with the following options:
   ** `-color` <face>: print the given text with <face>, most commonly `Error` or `Information`
   ** `-markup`: expand the markup strings in <text>
   ** `-debug`: print the given text to the `\*debug*` buffer
 * `nop`: does nothing, but as with every other commands, arguments may be
     evaluated. So nop can be used for example to execute a shell command
     while being sure that it's output will not be interpreted by kak.
     `:%sh{ echo echo tchou }` will echo tchou in Kakoune, whereas
     `:nop %sh{ echo echo tchou }` will not, but both will execute the
     shell command.

Multiple commands
~~~~~~~~~~~~~~~~~

Multiple commands can be separated either by new lines or by semicolons,
as such a semicolon must be escaped with `\;` to be considered as a literal
semicolon argument.

String syntax
~~~~~~~~~~~~~

When entering a command, parameters are separated by whitespace (shell like),
if you want to give parameters with spaces, you should quote them.

Kakoune support three string syntax:

 * `'strings'`: uninterpreted strings, you can use `\'` to escape the separator,
     every other char is itself.

 * `"strings"`: expanded strings, % strings (see <<Expansions>>) contained
     are expended. Use \% to escape a % inside them, and \\ to escape a slash.

 * `%{strings}`: these strings are very useful when entering commands

   - the `{` and `}` delimiters are configurable: you can use any non
     alphanumeric character. like `%[string]`, `%<string>`, `%(string)`,
     `%\~string~` or `%!string!`...
   - if the character following the % is one of {[(<, then the closing one is
     the matching }])> and the delimiters are not escapable but are nestable.
     for example `%{ roger {}; }` is a valid string, `%{ marcel \}` as well.

Expansions
^^^^^^^^^^

A special kind of `%{strings}` can be used, with a type between
`%` and the opening delimiter (which cannot be alphanumeric). These
strings are expanded according to their type.

For example `%opt{autoinfo}` is of type 'opt'. opt expansions are replaced
by the value of the given option (here `autoinfo`).

Supported types are:

 * `sh`: shell expansion, similar to posix shell $(...) construct, see
     <<Shell expansion>> for more details.
 * `reg`: register expansion, will be replaced by the content of the given
     register.
 * `opt`: option expansion, will be replaced with the value of the given
     option
 * `val`: value expansion, gives access to the environment variable available
     to the Shell expansion. The `kak_` prefix is not used there.
 * `arg`: argument expansion, gives access to the arguments of the current
     command, the content can be a number, or `@` for all arguments.

for example you can display last search pattern with

-------------
:echo %reg{/}
-------------

Shell expansion
^^^^^^^^^^^^^^^

The `%sh{...}` expansion replaces its content with the output of the shell
commands in it. It is similar to the shell $(...) syntax and is evaluated
only when needed.

for example: `%sh{ ls }` is replaced with the output of the ls command.

Some of Kakoune state is available through environment variables:

 * `kak_selection`: content of the main selection
 * `kak_selections`: content of the selection separated by colons, colons and backslashes in
        the selection contents are escaped with a backslash.
 * `kak_selection_desc`: range of the main selection, represented as `anchor,cursor`;
        anchor and cursor are in this format: `line.column` 
 * `kak_selections_desc`: range of the selecations separated by colons
 * `kak_bufname`: name of the current buffer
 * `kak_buffile`: full path of the file or same as `kak_bufname` when
       there's no associated file
 * `kak_buflist`: the current buffer list, each buffer separated by a colon
 * `kak_timestamp`: timestamp of the current buffer, the timestamp is an
       integer value which is incremented each time the buffer is modified.
 * `kak_runtime`: directory containing the kak binary
 * `kak_count`: count parameter passed to the command
 * `kak_opt_<name>`: value of option <name>
 * `kak_reg_<r>`: value of register <r>
 * `kak_socket`: filename of session socket (/tmp/kak-<session>)
 * `kak_session`: name of the current session
 * `kak_client`: name of current client
 * `kak_cursor_line`: line of the end of the main selection
 * `kak_cursor_column`: column of the end of the main selection (in byte)
 * `kak_cursor_char_column`: column of the end of the main selection (in character)
 * `kak_cursor_byte_offset`: offset of the main selection from the beginning of the buffer (in byte).
 * `kak_window_width`: width of the current kakoune window
 * `kak_window_height`: height of the current kakoune window
 * `kak_hook_param`: filtering text passed to the currently executing hook
 * `kak_client_env_<name>`: value of the <name> variable in the client environment.
	Example: $kak_client_env_SHELL is the SHELL variable

Note that in order to make only needed information available, Kakoune needs
to find the environment variable reference in the shell script executed.
Hence `%sh{ ./script.sh }` with `script.sh` referencing an environment
variable will not work.

For example you can print informations on the current file in the status
line using:

-------------------------------
:echo %sh{ ls -l $kak_bufname }
-------------------------------

Markup strings
^^^^^^^^^^^^^^

In certain context, kakoune can take a markup string, which is a string containing
formatting informations. In these strings, syntax `{facename}` will enable the
face _facename_ until another face gets activated (or the end of the string.
Literal `{` shall be written `\{`, and literal `\` that precede a `{` shall
be written `\\`

Configuration & Autoloading
---------------------------

Kakrc
~~~~~

If not launched with the `-n` switch, Kakoune will source the
`../share/kak/kakrc` file relative to the `kak` binary, which
will source additional files:

If the `$XDG_CONFIG_HOME/kak/autoload` directory exists, load every
`*.kak` files in it, and load recursively any subdirectory.

If it does not exists, falls back to the site wide autoload directory
in `../share/kak/autoload/`.

After that, if it exists, source the `$XDG_CONFIG_HOME/kak/kakrc` file
which should be used for user configuration.

In order to continue autoloading site-wide files with a local autoload
directory, just add a symbolic link to `../share/kak/autoload/` into
your local autoload directory.

Color Schemes
~~~~~~~~~~~~~

Kakoune ships with some color schemes that are installed to
`../share/kak/colors/`. If `$XDG_CONFIG_HOME/kak/colors/` is present
the builtin command `colorscheme` will offer completion for those
color schemes. If a scheme is duplicated in userspace it will take
precedence.

Options
-------

For user configuration, Kakoune supports options.

Options are typed, their type can be

 * `int`: an integer number
 * `bool`: a boolean value, `yes/true` or `no/false`
 * `str`: a string, some freeform text
 * `coord`: a line,column pair (separated by comma)
 * `regex`: as a string but the `set` commands will complain
   if the entered text is not a valid regex.
 * `{int,str}-list`: a list, elements are separated by a colon (:)
  if an element needs to contain a colon, it can be escaped with a
  backslash.
 * `range-faces`: a `:` separated list of a pairs of a buffer range
   (`<begin line>.<begin column>,<end line>.<end column>` or
   `<begin line>.<end line>+<length>`) and  a face (separated by `|`),
   except for the first element which is just the timestamp of the buffer.
 * `completions`: a `:` separated list of `<text>|<docstring>|<menu text>`
   candidates, except for the first element which follows the
   `<line>.<column>[+<length>]@<timestamp>` format to define where the
   completion apply in the buffer.
 * `enum(value1|value2|...)`: an enum, taking on of the given values
 * `flags(value1|value2|...)`: a set of flags, taking a combination
   of the given values joined by `|`.

Options value can be changed using the `set` commands:

------------------------------------------------------------------------------
:set [global,buffer,window] <option> <value> # buffer, window, or global scope
------------------------------------------------------------------------------

Option values can be different by scope, an option can have a global
value, a buffer value and a window value. The effective value of an
option depends on the current context. If we have a window in the
context (interactive edition for example), then the window value
(if any) is used, if not we try the buffer value (if we have a buffer
in the context), and if not we use the global value.

That means that two windows on the same buffer can use different options
(like different filetype, or different tabstop). However some options
might end up ignored if their scope is not in the command context:

Writing a file never uses the window options for example, so any
options related to writing wont be taken into account if set in the
window scope (`BOM` or `eolformat` for example).

New options can be declared using the `:decl` command:

---------------------------------------
:decl [-hidden] <type> <name> [<value>]
---------------------------------------

the `-hidden` parameter makes the option invisible in completion, but
still modifiable.

Some options are built in Kakoune, and can be used to control it's behaviour:

 * `tabstop` _int_: width of a tab character.
 * `indentwidth` _int_: width (in spaces) used for indentation.
   0 means a tab character.
 * `scrolloff` _coord_: number of lines,columns to keep visible around
   the cursor when scrolling.
 * `eolformat` _enum(lf|crlf)_: the format of end of lines when
   writing a buffer, this is autodetected on load; values of this option
   assigned to the `window` scope are ignored
 * `BOM` _enum(none|utf8)_: define if the file should be written
   with an unicode byte order mark. Values of this option assigned to the
   `window` scope are ignored
 * `readonly` _bool_: prevent modifications from being saved to disk, all
   buffers if set to `true` in the `global` scope, or current buffer if set in
   the `buffer` scope; values of this option assigned to the `window` scope are
   ignored
 * `incsearch` _bool_: execute search as it is typed
 * `aligntab` _bool_: use tabs for alignment command
 * `autoinfo` _flags(command|onkey|normal)_: display automatic information
   box in the enabled contexts.
 * `autoshowcompl` _bool_: automatically display possible completions when
   editing a prompt.
 * `ignored_files` _regex_: filenames matching this regex wont be considered
   as candidates on filename completion (except if the text being completed
   already matches it).
 * `disabled_hooks` _regex_: hooks whose group matches this regex wont be
   executed. For example indentation hooks can be disabled with '.*-indent'.
 * `filetype` _str_: arbitrary string defining the type of the file
   filetype dependant actions should hook on this option changing for
   activation/deactivation.
 * `path` _str-list_: directories to search for gf command.
 * `completers` _str-list_: completion systems to use for insert mode
   completion. given completers are tried in order until one generate some
   completion candidates. Existing completers are:
   - `word=all` or `word=buffer` which complete using words in all buffers
     (`word=all`) or only the current one (`word=buffer`)
   - `filename` which tries to detect when a filename is being entered and
     provides completion based on local filesystem.
   - `option=<opt-name>` where <opt-name> is a _completions_ option.
 * `static_words` _str-list_: list of words that are always added to completion
     candidates when completing words in insert mode.
 * `completions_extra_word_chars` _str_: a string containing all additional character
     that should be considered as word character for the purpose of insert mode
     completion.
 * `autoreload` _enum(yes|no|ask)_: auto reload the buffers when an external
   modification is detected.
 * `debug` _flags(hooks|shell|profile)_: dump various debug information in
   the `*debug*` buffer.
 * `idle_timeout` _int_: timeout, in milliseconds, with no user input that will
   trigger the `InsertIdle` and `NormalIdle` hooks. 
 * `fs_checkout_timeout` _int_: timeout, in milliseconds, between checks in
   normal mode of modifications of the file associated with the current buffer
   on the filesystem.
 * `modelinefmt` _string_: A format string used to generate the mode line, that
   string is first expanded as a command line would be (expanding `%...{...}`
   strings), then markup tags are applied (see <<Markup strings>>).
 * `ui_options`: colon separated list of key=value pairs that are forwarded to
   the user interface implementation. The NCurses UI support the following options:
   - `ncurses_set_title`: if `yes` or `true`, the terminal emulator title will
      be changed.
   - `ncurses_status_on_top`: if `yes`, or `true` the status line will be placed
     at the top of the terminal rather than at the bottom.
   - `ncurses_assistant`: specify the nice assistant you get in info boxes, can
      be 'clippy' (the default), 'cat' or 'none'
   - `ncurses_enable_mouse`: boolean option that enables mouse support
   - `ncurses_wheel_down_button` and `ncurses_wheel_up_button`: specify which
      button send for wheel down/up events.
   - `ncurses_buffer_padding_str`: string that will be used to mark the
      end of the buffer.
   - `ncurses_buffer_padding_type`: if set to `fill`, the padding string
      will fill the entire space between the end of the buffer and the
      bottom of the current window, if set to `single` the padding
      string will be inserted once at the end of the buffer. A value of
      `off` disables any kind of padding.

Faces
-----

A Face refers how the specified text is displayed. A face has a foreground
color, a background color, and some attributes.

Faces can be defined and modified with the face command:

-----------------------
:face <name> <facespec>
-----------------------

Any place requiring a face can take either a face name defined with the `face`
command or a direct face description (called _facespec_) with the following
syntax:

--------------------------------
fg_color[,bg_color][+attributes]
--------------------------------

fg_color and bg_color can be:

 * A named color: `black, red, green, yellow, blue, magenta, cyan, white`.
 * `default`, which keeps the existing color
 * An rgb color: `rgb:RRGGBB`, with RRGGBB the hexadecimal value of the color.

not specifying bg_color uses `default`

attributes is a string of letters each defining an attributes:

 * `u`: Underline
 * `r`: Reverse
 * `b`: Bold
 * `B`: Blink
 * `d`: Dim
 * `i`: Italic
 * `e`: Exclusive, override previous faces instead of merging with them

Using named faces instead of facespec permits to change the effective faces
afterwards.

There are some builtins faces used by internal Kakoune functionalities:

 * `Default`: default colors
 * `PrimarySelection`: main selection face for every selected character except
     the cursor
 * `SecondarySelection`: secondary selection face for every selected character
     except the cursor
 * `PrimaryCursor`: cursor of the primary selection
 * `SecondaryCursor`: cursor of the secondary selection
 * `LineNumbers`: face used by the number_lines highlighter
 * `LineNumberAbsolute`: face used to highlight the line number of the main
     selection
 * `MenuForeground`: face for the selected element in menus
 * `MenuBackground`: face for the not selected elements in menus
 * `Information`: face for the informations windows and information messages
 * `Error`: face of error messages
 * `StatusLine`: face used for the status line
 * `StatusCursor`: face used for the status line cursor
 * `Prompt`: face used prompt displayed on the status line
 * `MatchingChar`: face used by the show_matching highlighter
 * `Search`: face used to highlight search results
 * `BufferPadding`: face applied on the characters that follow the last line of a buffer

Advanced topics
---------------

Registers
~~~~~~~~~

Registers are named lists of text. They are used for various purposes, like
storing the last yanked text, or the captured groups associated with the
selections.

Yanking and pasting uses the register `"`, however most commands using a register
can have their default register overridden by using the `"` key followed by the
register. For example `"sy` will yank (`y` command) in the `s` register. `"sp`
will paste from the `s` register.

While in insert mode or in a prompt, `ctrl-r` followed by a register name
(one character) inserts it.

For example, `ctrl-r` followed by " will insert the currently yanked text.
`ctrl-r` followed by 2 will insert the second capture group from the last regex
selection.

Registers are lists, instead of simply text in order to interact well with
multiselection. Each selection has its own captures or yank buffer.

Alternate names
^^^^^^^^^^^^^^^

non alphanumeric registers have an alternative name that can be used
in contexts where only alphanumeric identifiers are possible.

Special registers
^^^^^^^^^^^^^^^^^

Some registers are not general purposes, they cannot be written to, but they
contain some special data:

 * `%` (`percent`): current buffer name
 * `.` (`dot`): current selection contents
 * `#` (`hash`): selection indices (first selection has 1, second has 2, ...)
 * `_` (`underscore`): null register, always empty

Default registers
^^^^^^^^^^^^^^^^^

Most commands using a register default to a specific one if not specified:

 * `"` (`dquote`): default yank register, used by yanking and pasting commands like `y`, `p` and `R`
 * `/` (`slash`): default search register, used by regex based commands like `s`, `*` or `/`
 * `@` (`arobase`): default macro register, used by `q` and `Q`
 * `^` (`caret`): default mark register, used by `z` and `Z`
 * `|` (`pipe`): default shell command register, used by command that spawn a subshell such as `|`, `<a-|>`, `!` or `<a-!>`

Macros
~~~~~~

Kakoune can record and replay a sequence of key presses.

Macros are recorded with the `Q` key, and are stored by default in the `@`
register. Another register can be chosen by with hitting `"<reg>` before
the `Q` key.

To replay a macro, use the `q` key.

Search selection
~~~~~~~~~~~~~~~~

Using the `*` key, you can set the search pattern to the current selection.
This tries to be intelligent. It will for example detect if the current selection
begins and/or ends at word boundaries and set the search pattern accordingly.

with `alt-*` you can set the search pattern to the current selection without
Kakoune trying to be smart.

Regex syntax
~~~~~~~~~~~~

The regex syntax supported by Kakoune is the Perl syntax currently provided 
by Boost :
http://www.boost.org/doc/libs/release/libs/regex/doc/html/boost_regex/syntax/perl_syntax.html[Perl Regular Expression Syntax].

Exec and Eval
~~~~~~~~~~~~~

the `:exec` and `:eval` commands can be used for running Kakoune commands.
`:exec` runs keys as if they were pressed, whereas `:eval` executes its given
paremeters as if they were entered in the command prompt. By default,
they do their execution in the context of the current client.

These two commands also save the following registers, who are then restored
when the commands have been executed: `/`, `"`, `|`, `^`, `@`.

Some parameters provide a way to change the context of execution:

 * `-client <name>`: execute in the context of the client named <name>
 * `-try-client <name>`: execute in the context of the client named
     <name> if such client exists, or else in the current context.
 * `-draft`: execute in a copy of the context of the selected client
     modifications to the selections or input state will not affect
     the client. This permits to make some modification to the buffer
     without modifying the user's selection.
 * `-itersel` (requires `-draft`): execute once per selection, in a
     context with only the considered selection. This permits to avoid
     cases where the selections may get merged.
 * `-buffer <names>`: execute in the context of each buffers in the
     comma separated list <names>, '*' as a name can be used to iterate
     on all buffers.
 * `-no-hooks`: disable hook execution while executing the keys/commands
 * `-with-maps`: use user key mapping in `:exec` instead of built in keys.
 * `-save-regs <regs>`: regs is a string of registers to be restored after
    execution (overwrites the list of registers saved by default)

The execution stops when the last key/command is reached, or an error
is raised.

Key parameters get concatenated, so the following commands are equivalent:

----------------------
:exec otest<space>1
:exec o test <space> 1
----------------------

Insert mode completion
~~~~~~~~~~~~~~~~~~~~~~

Kakoune can propose completions while inserting text, the `completers` option
controls automatic completion, which kicks in when a certain idle timeout is
reached (100 milliseconds). Insert mode completion can be explicitly triggered
using *control-x*, followed, by:

 * *f* : filename completion
 * *w* : buffer word completion
 * *l* : buffer line completion

Completion candidates can be selected using `ctrl-n` and `ctrl-p`.

Escape to normal mode
~~~~~~~~~~~~~~~~~~~~~

From insert mode, pressing `<a-;>` allows you to execute a single normal mode
command. This provides a few advantages:

 * The selections are not modified: when leaving insert mode using `<esc>` the
   selections can change, for example when insert mode was entered with `a` the
   cursor will go back one char. Or if on an end of line the cursor will go back
   left (if possible).

 * The modes are nested: that means the normal mode can enter prompt (with `:`),
   or any other modes (using `:onkey` or `:menu` for example), and these modes
   will get back to the insert mode afterwards.

This feature is tailored for scripting/macros, as it provides a more predictable
behaviour than leaving insert mode with `<esc>`, executing normal mode command
and entering back insert mode (with which binding ?)

Highlighters
~~~~~~~~~~~~

Manipulation of the displayed text is done through highlighters, which can be added
or removed with the command

-----------------------------------------------------
:addhl <highlighter_name> <highlighter_parameters...>
-----------------------------------------------------

and

----------------------
:rmhl <highlighter_id>
----------------------

`highlighter_id` is a name generated by the highlighter specified with `highlighter_name`,
possibly dependent on the parameters. Use command completion on rmhl to see the existing
highlighters id.

general highlighters are:

 * `regex <ex> <capture_id>:<face>...`: highlight a regex, takes the regex as
       first parameter, followed by any number of face parameters.
       For example: `:addhl regex (\hTODO:)?[^\n] 0:cyan 1:yellow,red`
       will highlight C++ style comments in cyan, with an eventual 'TODO:' in
       yellow on red background.
 * `dynregex`: Similar to regex, but expand (like a command parameter would) the
       given expression before building a regex from the result.
 * `flag_lines <flag> <option_name>`: add a column in front of text, and display the
       given flag in it for everly line contained in the int-list option named
       <option_name>.
 * `show_matching`: highlight matching char of the character under the selections
       cursor using `MatchingChar` face.
 * `number_lines \<-relative> \<-hlcursor> \<-separator <separator text> >`: show line numbers.
       The -relative switch will show line numbers relative to the main cursor line, the
       -hlcursor switch will highlight the cursor line with a separate face. With the
       -separator switch one can specify a string to separate the line numbers column with
       the rest of the buffer, default is `|`.
 * `fill <face>`: fill using given face, mostly useful with <<regions-highlighters,Regions highlighters>>
 * `ranges <option_name>`: use the data in the range-faces option of the given name to highlight the buffer.

Highlighting Groups
^^^^^^^^^^^^^^^^^^^

the `group` highlighter is a container for other highlighters. You can add
a group to the current window using

------------------
addhl group <name>
------------------

and then the `-group` switch of `addhl` provides a mean to add highlighters
inside this group.

--------------------------------------
addhl -group <name> <type> <params>...
--------------------------------------

groups can contain other groups, the `-group` switch can be used to define a path.

------------------------------------------------
addhl -group <name> group <subname>
addhl -group <name>/<subname> <type> <params>...
------------------------------------------------

[[regions-highlighters]]
Regions highlighters
^^^^^^^^^^^^^^^^^^^^

A special highlighter provides a way to segment the buffer into regions, which are
to be highlighted differently.

A region is defined by 4 parameters:

------------------------------------
<name> <opening> <closing> <recurse>
------------------------------------

`name` is user defined, `opening`, `closing` and `recurse` are regexes.

 * `opening` defines the region start text
 * `closing` defines the region end text
 * `recurse` defines the text that matches recursively an end token into the region.

`recurse` is useful for regions that can be nested, for example the `%sh{ ... }`
construct in kakoune accept nested `{ ... }` so `%sh{ ... { ... } ... }` is valid.
this region can be defined with:

------------------------
shell_expand %sh\{ \} \{
------------------------

Regions are used in the `regions` highlighter which can take any number
of regions.

-----------------------------------------------------------------------
addhl regions <name> <region_name1> <opening1> <closing1> <recurse1>  \
                     <region_name2> <opening2> <closing2> <recurse2>...
-----------------------------------------------------------------------

defines multiple regions in which other highlighters can be added

-------------------------------------
addhl -group <name>/<region_name> ...
-------------------------------------

Regions are matched using the left-most rule: the left-most region opening starts
a new region. when a region closes, the closest next opening start another region.

That matches the rule governing most programming language parsing.

`regions` also supports a `-default <default_region>` switch to define the
default region, when no other region matches the current buffer range.

Most programming languages can then be properly highlighted using a `regions`
highlighter as root:

-----------------------------------------------------------------
addhl regions -default code <lang> \
    string <str_opening> <str_closing> <str_recurse> \
    comment <comment_opening> <comment_closing> <comment_recurse>

addhl -group <lang>/code ...
addhl -group <lang>/string ...
addhl -group <lang>/comment ...
-----------------------------------------------------------------

Shared Highlighters
^^^^^^^^^^^^^^^^^^^

Highlighters are often defined for a specific filetype, and it makes then sense to
share the highlighters between all the windows on the same filetypes.

A shared highlighter can be defined with the `:addhl` command

------------------------------
addhl -group /<group_name> ...
------------------------------

when the group switch values starts with a '/', it references a group in the
shared highlighters, rather than the window highlighters.

The common case would be to create a named shared group, and then fill it
with highlighters:

---------------------------
addhl -group / group <name>
addhl -group /name regex ...
---------------------------

It can then be referenced in a window using the `ref` highlighter.

----------------
addhl ref <name>
----------------

the `ref` can reference any named highlighter in the shared namespace.

Hooks
~~~~~

Commands can be registered to be executed when certain events arise.
To register a hook use the hook command.

-----------------------------------------------------------------------
:hook [-group <group>] <scope> <hook_name> <filtering_regex> <commands>
-----------------------------------------------------------------------

`<scope>` can be either global, buffer or window (or any of their prefixes).
Scopes are hierarchical, meaning that a Window calling a hook will
execute its own, the buffer ones and the global ones.

`<command>` is a string containing the commands to execute when the hook is
called.

For example to automatically use line numbering with .cc files,
use the following command:

-----------------------------------------------------
:hook global WinCreate .*\.cc %{ addhl number_lines }
-----------------------------------------------------

if `<group>` is given, make this hook part of the named group. groups
are used for removing hooks with the `rmhooks` command

-----------------------
rmhooks <scope> <group>
-----------------------

will remove every hooks in `<scope>` that are part of the given group.

existing hooks are:

 * `NormalIdle`: A certain duration has passed since last key was pressed in
       normal mode.
 * `NormalBegin`: Entering normal mode
 * `NormalEnd`: Leaving normal mode
 * `NormalKey`: A key is received in normal mode, the key is used for filtering
 * `InsertIdle`: A certain duration has passed since last key was pressed in
       insert mode.
 * `InsertBegin`: Entering insert mode
 * `InsertEnd`: Leaving insert mode
 * `InsertKey`: A key is received in insert mode, the key is used for filtering
 * `InsertChar`: A character is inserted in insert mode, the character is used
       for filtering
 * `InsertMove`: The cursor moved (without inserting) in insert mode, the key
       that triggered the move is used for filtering
 * `WinCreate`: A window was created, the filtering text is the buffer name
 * `WinClose`: A window was destroyed, the filtering text is the buffer name
 * `WinDisplay`: A window was bound a client, the filtering text is the buffer
       name
 * `WinResize`: A window resized, the filtering text is '<line>.<column>'
 * `WinSetOption`: An option was set in a window context, the filtering text
       is '<option_name>=<new_value>'
 * `BufSetOption`: An option was set in a buffer context, the filtering text
       is '<option_name>=<new_value>'
 * `BufNew`: A buffer for a new file has been created, filename is used for
       filtering
 * `BufOpen`: A buffer for an existing file has been created, filename is
       used for filtering
 * `BufCreate`: A buffer has been created, filename is used for filtering
 * `BufWritePre`: Executed just before a buffer is written, filename is
       used for filtering.
 * `BufWritePost`: Executed just after a buffer is written, filename is
       used for filtering.
 * `BufClose`: Executed when a buffer is deleted, while it is still valid.
 * `BufOpenFifo`: Executed when a buffer opens a fifo.
 * `BufReadFifo`: Executed after some data has been read from a fifo and
       inserted in the buffer.
 * `BufCloseFifo`: Executed when a fifo buffer closes its fifo file descriptor
       either because the buffer is being deleted, or because the writing
       end has been closed.
 * `RuntimeError`: an error was encountered while executing an user command
       the error message is used for filtering
 * `KakBegin`: Kakoune started, this is called just after reading the user
       configuration files
 * `KakEnd`: Kakoune is quitting.
 * `FocusIn`: On supported clients, triggered when the client gets focused.
       the filtering text is the client name.
 * `FocusOut`: On supported clients, triggered when the client gets unfocused.
       the filtering text is the client name.
 * `InsertCompletionShow`: Triggered when the insert completion menu gets
       displayed.
 * `InsertCompletionHide`: Triggered when the insert completion menu gets
       hidden.

When not specified, the filtering text is an empty string.

Key Mapping
~~~~~~~~~~~

You can redefine a key's meaning using the map command

--------------------------------
:map <scope> <mode> <key> <keys>
--------------------------------

with `scope` being one of `global`, `buffer` or `window` (or any prefix),
mode being `insert`, `normal`, `prompt`, `menu` or `user` (or any prefix), `key` being
a single key name and `keys` a list of keys.

`user` mode allows for user mapping behind the `,` key. Keys will be executed in
normal mode.

Mappings can be removed with the unmap command

----------------------------------------
:unmap <scope> <mode> <key> [<expected>]
----------------------------------------

If `<expected>` is specified, unmapping will only proceed if the current
mapping matches the expected keys.

Defining Commands
~~~~~~~~~~~~~~~~~

New commands can be defined using the `:def` command.

------------------------------
:def <command_name> <commands>
------------------------------

`<commands>` is a string containing the commands to execute.

`def` can also takes some flags:

 * `-params <num>`: the command accept <num> parameters, with <num>
    either a number, or of the form <min>..<max>, with both <min> and
    <max> omittable.
 * `-file-completion`: try file completion on any parameter passed
    to this command
 * `-client-completion`: try client name completion on any parameter
    passed to this command
 * `-buffer-completion`: try buffer name completion on any parameter
    passed to this command
 * `-shell-completion`: following string is a shell command which takes
    parameters as positional params and output one completion candidate
    per line.
 * `-allow-override`: allow the new command to replace an existing one
    with the same name.
 * `-hidden`: do not show the command in command name completions
 * `-docstring`: define the documentation string for the command

Using shell expansion permits to define complex commands or to access
Kakoune state:

------------------------------------------------------
:def print_selection %{ echo %sh{ ${kak_selection} } }
------------------------------------------------------

Some helper commands can be used to define composite commands:

 * `prompt <prompt> <register> <command>`: Prompt the user for a string, when
     the user validates, store the result in given <register> and run <commmand>.
     the -init <str> switch allows setting initial content and -password allow
     not to show the entered text (and clears the register after command execution).
 * `onkey <register> <command>`: Wait for next key from user, writes it into given
     <register> and execute commands.
 * `menu <label1> <commands1> <label2> <commands2>...`: display a menu using
     labels, the selected label's commands are executed.
     `menu` can take a -auto-single argument, to automatically run commands
     when only one choice is provided. and a -select-cmds argument, in which
     case menu takes three argument per item, the last one being a command
     to execute when the item is selected (but not validated).
 * `info <text>`: display text in an information box, at can take a -anchor
     option, which accepts `left`, `right` and `cursor` as value, in order to
     specify where the info box should be anchored relative to the main selection.
 * `try <commands> catch <on_error_commands>`: prevent an error in <commands>
     from aborting the whole commands execution, execute <on_error_commands>
     instead. If nothing is to be done on error, the catch part can be ommitted.
 * `reg <name> <content>`: set register <name> to <content>
 * `select <anchor_line>.<anchor_column>,<cursor_line>.<cursor_column>:...`:
     replace the current selections with the one described in the argument
 * `debug {info,buffers,options,memory,shared-strings}`: print some debug
     information in the `*debug*` buffer

Note that these commands are available in interactive command mode, but are
not that useful in this context.

Aliases
~~~~~~~

With `:alias` commands can be given additional names. Aliases are scoped, so
that an alias can refer to one command for a buffer, and to another for another
buffer.

--------------------------------
:alias <scope> <alias> <command>
--------------------------------

with `<scope>` being `global`, `buffer` or `window`, will define `<alias>` as
an alias for `<command>`

-------------------------------------
:unalias <scope> <alias> [<expected>]
-------------------------------------

will remove the given alias in the given scope. If `<expected>` is specified
the alias will only be removed if its current value is `<expected>`.

FIFO Buffer
~~~~~~~~~~~

the `:edit` command can take a `-fifo` parameter:

---------------------------------------------
:edit -fifo <filename> [-scroll] <buffername>
---------------------------------------------

In this case, a buffer named `<buffername>` is created which reads its content
from fifo `<filename>`. When the fifo is written to, the buffer is automatically
updated.

if the `-scroll` switch is specified, the initial cursor position will be made
such as the window displaying the buffer will scroll as new data is read.

This is very useful for running some commands asynchronously while displaying
their result in a buffer. See `rc/make.kak` and `rc/grep.kak` for examples.

When the buffer is deleted, the fifo will be closed, so any program writing
to it will receive `SIGPIPE`. This is usefull as it permits to stop the writing
program when the buffer is deleted.

Menus
~~~~~

When a menu is displayed, you can use `j`, `<ctrl-n>` or `<tab>` to select the next
entry, and `k`, `<ctrl-p>` or `<shift-tab>` to select the previous one.

Using the `/` key, you can enter some regex in order to restrict available choices
to the matching ones.