Have 38 registered hooks:

after-poll
----------
File: ~/.sup/hooks/after-poll.rb
Executes immediately after a poll for new messages completes.
Variables:
                   num: the total number of new messages added in this poll
             num_inbox: the number of new messages added in this poll which
                        appear in the inbox (i.e. were not auto-archived).
             num_total: the total number of messages
       num_inbox_total: the total number of new messages in the inbox.
num_inbox_total_unread: the total number of unread messages in the inbox
           num_updated: the total number of updated messages
           num_deleted: the total number of deleted messages
                labels: the labels that were applied
         from_and_subj: an array of (from email address, subject) pairs
   from_and_subj_inbox: an array of (from email address, subject) pairs for
                        only those messages appearing in the inbox

async-edit
----------
File: ~/.sup/hooks/async-edit.rb
Runs when 'H' is pressed in async edit mode. You can run whatever code
you want here - though the default case would be launching a text
editor. Your hook is assumed to not block, so you should use exec() or
fork() to launch the editor.

Once the hook has returned then sup will be responsive as usual. You will
still need to press 'E' to exit this buffer and send the message.

Variables:
file_path: The full path to the file containing the message to be edited.

Return value: None

attribution
-----------
File: ~/.sup/hooks/attribution.rb
Generates an attribution ("Excerpts from Joe Bloggs's message of Fri Jan 11 09:54:32 -0500 2008:").
Variables:
  message: a message object representing the message being replied to
    (useful values include message.from.name and message.date)
Return value:
  A string containing the text of the quote line (can be multi-line)

before-add-message
------------------
File: ~/.sup/hooks/before-add-message.rb
Executes immediately before a message is added to the index.
Variables:
  message: the new message

before-edit
-----------
File: ~/.sup/hooks/before-edit.rb
Modifies message body and headers before editing a new message. Variables
should be modified in place.
Variables:
	header: a hash of headers. See 'signature' hook for documentation.
	body: an array of lines of body text.
Return value:
	none

before-poll
-----------
File: ~/.sup/hooks/before-poll.rb
Executes immediately before a poll for new messages commences.
No variables.

bounce-command
--------------
File: ~/.sup/hooks/bounce-command.rb
Determines the command used to bounce a message.
Variables:
      from: The From header of the message being bounced
            (eg: likely _not_ your address).
        to: The addresses you asked the message to be bounced to as an array.
Return value:
  A string representing the command to pipe the mail into.  This
  should include the entire command except for the destination addresses,
  which will be appended by sup.

check-attachment
----------------
File: ~/.sup/hooks/check-attachment.rb
Do checks on the attachment filename
Variables:
	filename: the name of the attachment
Return value:
    A String (single line) containing a message why this attachment is not optimal
    to be attached.
    If it is ok just return an empty string or nil

crypto-mode
-----------
File: ~/.sup/hooks/crypto-mode.rb
Modifies cryptography settings based on header and message content, before
editing a new message. This can be used to set, for example, default cryptography
settings.
Variables:
    header: a hash of headers. See 'signature' hook for documentation.
    body: an array of lines of body text.
    crypto_selector: the UI element that controls the current cryptography setting.
Return value:
     none

custom-search
-------------
File: ~/.sup/hooks/custom-search.rb
Executes before a string search is applied to the index,
returning a new search string.
Variables:
  subs: The string being searched.

detailed-headers
----------------
File: ~/.sup/hooks/detailed-headers.rb
Add or remove headers from the detailed header display of a message.
Variables:
  message: The message whose headers are to be formatted.
  headers: A hash of header (name, value) pairs, initialized to the default
           headers.
Return value:
  None. The variable 'headers' should be modified in place.

extra-contact-addresses
-----------------------
File: ~/.sup/hooks/extra-contact-addresses.rb
A list of extra addresses to propose for tab completion, etc. when the
user is entering an email address. Can be plain email addresses or can
be full "User Name <email@domain.tld>" entries.

Variables: none
Return value: an array of email address strings.

forward-attribution
-------------------
File: ~/.sup/hooks/forward-attribution.rb
Generates the attribution for the forwarded message
(["--- Begin forwarded message from John Doe ---",
"--- End forwarded message ---"])
Variables:
  message: a message object representing the message being replied to
    (useful values include message.from.mediumname and message.date)
Return value:
  A list containing two strings: the text of the begin line and the text of the end line

goto
----
File: ~/.sup/hooks/goto.rb
Open the uri given as a parameter.
Variables:
      uri: The uri
Return value:
  None.

gpg-expand-keys
---------------
File: ~/.sup/hooks/gpg-expand-keys.rb
Runs when the list of encryption recipients is created, allowing you to
replace a recipient with one or more GPGME recipients. For example, you could
replace the email address of a mailing list with the key IDs that belong to
the recipients of that list. This is essentially what GPG groups do, which
are not supported by GPGME.

Variables:
recipients: an array of recipients of the current email

Return value: an array of recipients (email address or GPG key ID) to encrypt
the email for

gpg-options
-----------
File: ~/.sup/hooks/gpg-options.rb
Runs before gpg is called, allowing you to modify the options (most
likely you would want to add something to certain commands, like
{:always_trust => true} to encrypting a message, but who knows).

Variables:
operation: what operation will be done ("sign", "encrypt", "decrypt" or "verify")
options: a dictionary of values to be passed to GPGME

Return value: a dictionary to be passed to GPGME

index-mode-date-widget
----------------------
File: ~/.sup/hooks/index-mode-date-widget.rb
Generates the per-thread date widget for each thread.
Variables:
  thread: The message thread to be formatted.

index-mode-size-widget
----------------------
File: ~/.sup/hooks/index-mode-size-widget.rb
Generates the per-thread size widget for each thread.
Variables:
  thread: The message thread to be formatted.

keybindings
-----------
File: ~/.sup/hooks/keybindings.rb
Add custom keybindings.
Methods:
  modes: Hash from mode names to mode classes.
  global_keymap: The top-level keymap.

label-list-filter
-----------------
File: ~/.sup/hooks/label-list-filter.rb
Filter the label list, typically to sort.
Variables:
  counted: an array of counted labels.
Return value:
  An array of counted labels with sort_by output structure.

label-list-format
-----------------
File: ~/.sup/hooks/label-list-format.rb
Create the sprintf format string for label-list-mode.
Variables:
  width: the maximum label width
  tmax: the maximum total message count
  umax: the maximum unread message count
Return value:
  A format string for sprintf

mark-as-spam
------------
File: ~/.sup/hooks/mark-as-spam.rb
This hook is run when a thread is marked as spam
Variables:
  thread: The message thread being marked as spam.

mentions-attachments
--------------------
File: ~/.sup/hooks/mentions-attachments.rb
Detects if given message mentions attachments the way it is probable
that there should be files attached to the message.
Variables:
	header: a hash of headers. See 'signature' hook for documentation.
	body: an array of lines of body text.
Return value:
	True if attachments are mentioned.

mime-decode
-----------
File: ~/.sup/hooks/mime-decode.rb
Decodes a MIME attachment into text form. The text will be displayed
directly in Sup. For attachments that you wish to use a separate program
to view (e.g. images), you should use the mime-view hook instead.

Variables:
   content_type: the content-type of the attachment
        charset: the charset of the attachment, if applicable
       filename: the filename of the attachment as saved to disk
  sibling_types: if this attachment is part of a multipart MIME attachment,
                 an array of content-types for all attachments. Otherwise,
                 the empty array.
Return value:
  The decoded text of the attachment, or nil if not decoded.

mime-view
---------
File: ~/.sup/hooks/mime-view.rb
Views a non-text MIME attachment. This hook allows you to run
third-party programs for attachments that require such a thing (e.g.
images). To instead display a text version of the attachment directly in
Sup, use the mime-decode hook instead.

Note that by default (at least on systems that have a run-mailcap command),
Sup uses the default mailcap handler for the attachment's MIME type. If
you want a particular behavior to be global, you may wish to change your
mailcap instead.

Variables:
   content_type: the content-type of the attachment
       filename: the filename of the attachment as saved to disk
Return value:
  True if the viewing was successful, false otherwise. If false, calling
  /usr/bin/run-mailcap will be tried.

publish
-------
File: ~/.sup/hooks/publish.rb
Executed when a message or a chunk is requested to be published.
Variables:
     chunk: Redwood::Message or Redwood::Chunk::* to be published.
Return value:
  None.

reply-from
----------
File: ~/.sup/hooks/reply-from.rb
Selects a default address for the From: header of a new reply.
Variables:
  message: a message object representing the message being replied to
    (useful values include message.recipient_email, message.to, and message.cc)
Return value:
  A Person to be used as the default for the From: header, or nil to use the
  default behavior.

reply-to
--------
File: ~/.sup/hooks/reply-to.rb
Set the default reply-to mode.
Variables:
  modes: array of valid modes to choose from, which will be a subset of
             [:sender, :recipient, :list, :all, :user]
         The default behavior is equivalent to
             ([:list, :sender, :recipent] & modes)[0]
Return value:
  The reply mode you desire, or nil to use the default behavior.

search-list-filter
------------------
File: ~/.sup/hooks/search-list-filter.rb
Filter the search list, typically to sort.
Variables:
  counted: an array of counted searches.
Return value:
  An array of counted searches with sort_by output structure.

search-list-format
------------------
File: ~/.sup/hooks/search-list-format.rb
Create the sprintf format string for search-list-mode.
Variables:
  n_width: the maximum search name width
  tmax: the maximum total message count
  umax: the maximum unread message count
  s_width: the maximum search string width
Return value:
  A format string for sprintf

sendmail
--------
File: ~/.sup/hooks/sendmail.rb
Sends the given mail. If this hook doesn't exist, the sendmail command
configured for the account is used.
The message will be saved after this hook is run, so any modification to it
will be recorded.
Variables:
    message: RMail::Message instance of the mail to send
    account: Account instance matching the From address
Return value:
     True if mail has been sent successfully, false otherwise.

shutdown
--------
File: ~/.sup/hooks/shutdown.rb
Executes when sup is shutting down. May be run when sup is crashing,
so don't do anything too important. Run before the label, contacts,
and people are saved.
No variables.
No return value.

sig-output
----------
File: ~/.sup/hooks/sig-output.rb
Runs when the signature output is being generated, allowing you to
add extra information to your signatures if you want.

Variables:
signature: the signature object (class is GPGME::Signature)
from_key: the key that generated the signature (class is GPGME::Key)

Return value: an array of lines of output

signature
---------
File: ~/.sup/hooks/signature.rb
Generates a message signature.
Variables:
      header: an object that supports string-to-string hashtable-style access
              to the raw headers for the message. E.g., header["From"],
              header["To"], etc.
  from_email: the email part of the From: line, or nil if empty
  message_id: the unique message id of the message
Return value:
  A string (multi-line ok) containing the text of the signature, or nil to
  use the default signature, or :none for no signature.

startup
-------
File: ~/.sup/hooks/startup.rb
Executes at startup
No variables.
No return value.

status-bar-text
---------------
File: ~/.sup/hooks/status-bar-text.rb
Sets the status bar. The default status bar contains the mode name, the buffer
title, and the mode status. Note that this will be called at least once per
keystroke, so excessive computation is discouraged.

Variables:
         num_inbox: number of messages in inbox
  num_inbox_unread: total number of messages marked as unread
         num_total: total number of messages in the index
          num_spam: total number of messages marked as spam
             title: title of the current buffer
              mode: current mode name (string)
            status: current mode status (string)
Return value: a string to be used as the status bar.

terminal-title-text
-------------------
File: ~/.sup/hooks/terminal-title-text.rb
Sets the title of the current terminal, if applicable. Note that this will be
called at least once per keystroke, so excessive computation is discouraged.

Variables: the same as status-bar-text hook.
Return value: a string to be used as the terminal title.

time-to-nice-string
-------------------
File: ~/.sup/hooks/time-to-nice-string.rb
Formats time nicely as string.
Variables:
  time: The Time instance to be formatted.
  from: The Time instance providing the reference point (considered "now").