reference notmuch_init_file now in notmuch-emacs.mdwn

[notmuch-wiki] / emacstips.mdwn

[[!img notmuch-logo.png alt="Notmuch logo" class="left"]]
# Tips and Tricks for using Notmuch with Emacs

Here are some tips and tricks for using Notmuch with Emacs. See the [[Notmuch
Emacs Interface|notmuch-emacs]] page for basics.

[[!toc levels=2]]

## Issues with Emacs 24

If notmuch-show-mode behaves badly for you in emacs 24.x try adding one of

        (setq gnus-inhibit-images nil)

or

        (require 'gnus-art)

to your .emacs file.

## Controlling external handlers for attachements

You can choose e.g. which pdf viewer to invoke from notmuch-show mode by
adding a .mailcap file in your home directory. Here is an example:

    application/pdf; /usr/bin/mupdf %s; test=test "$DISPLAY" != ""; description=Portable Document Format; nametemplate=%s.pdf
    application/x-pdf; /usr/bin/mupdf %s; test=test "$DISPLAY" != ""; description=Portable Document Format; nametemplate=%s.pdf

## Overwriting the sender address

If you want to always use the same sender address, then the following
defadvice can help you.

       (defadvice notmuch-mua-reply (around notmuch-fix-sender)
         (let ((sender "Max Monster <max.monster@example.com>"))
           ad-do-it))
       (ad-activate 'notmuch-mua-reply)

## Initial cursor position in notmuch 0.15 hello window

In notmuch version 0.15 emacs client the handling of cursor position in
notmuch hello window has been simplified to a version which suits best
most cases.

Initially the cursor is positioned at the beginning of buffer.

Some users liked the "ancient" version where cursor was moved to the
first `Saved searches` button.

Add the following code to your notmuch emacs configuration file in
case you want this behaviour:

        (add-hook 'notmuch-hello-refresh-hook
                  (lambda ()
                    (if (and (eq (point) (point-min))
                             (search-forward "Saved searches:" nil t))
                        (progn
                          (forward-line)
                          (widget-forward 1))
                      (if (eq (widget-type (widget-at)) 'editable-field)
                          (beginning-of-line)))))

## Add a key binding to add/remove/toggle a tag

The `notmuch-{search,show,tree}-tag` functions are very useful for
making quick tag key bindings.  The arguments to these functions have
changed as notmuch has evolved but the following should work on all
versions of notmuch from 0.13 on.  These functions take a list of
tag changes as argument. For example, an argument of (list "+spam"
"-inbox") adds the tag spam and deletes the tag inbox. Note the
argument must be a list even if there is only a single tag change
e.g., use (list "+deleted") to add the deleted tag.

For instance, here's an example of how to make a key binding to add
the "spam" tag and remove the "inbox" tag in notmuch-show-mode:

        (define-key notmuch-show-mode-map "S"
          (lambda ()
            "mark message as spam"
            (interactive)
            (notmuch-show-tag (list "+spam" "-inbox"))))

You can do the same for threads in `notmuch-search-mode` by just
replacing "show" with "search" in the keymap and called functions, or
for messages in `notmuch-tree-mode` by replacing "show" by "tree". If
you want to tag a whole thread in `notmuch-tree-mode` use
`notmuch-tree-tag-thread` instead of `notmuch-tree-tag`.

You may also want the function in search mode apply to the all threads
in the selected region (if there is one). For notmuch prior to 0.17
this behaviour will occur automatically with the functions given
above. To get this behaviour on 0.17+ do the following:

        (define-key notmuch-search-mode-map "S"
          (lambda (&optional beg end)
            "mark thread as spam"
            (interactive (notmuch-search-interactive-region))
            (notmuch-search-tag (list "+spam" "-inbox") beg end)))

The analogous functionality in notmuch-tree is currently missing.

The definitions above make use of a lambda function, but you could
also define a separate function first:

        (defun notmuch-show-tag-spam ()
          "mark message as spam"
          (interactive)
          (notmuch-show-add-tag (list "+spam" "-inbox")))

        (define-key notmuch-show-mode-map "S" 'notmuch-show-tag-spam)

Here's a more complicated example of how to add a toggle "deleted"
key:

        (define-key notmuch-show-mode-map "d"
          (lambda ()
            "toggle deleted tag for message"
            (interactive)
            (if (member "deleted" (notmuch-show-get-tags))
                (notmuch-show-tag (list "-deleted"))
              (notmuch-show-tag (list "+deleted")))))

## Adding many tagging keybindings

If you want to have have many tagging keybindings, you can save the typing
the few lines of  boilerplate for every binding (for versions before 0.12,
you will need to change notmuch-show-apply-tag-macro).

    (eval-after-load 'notmuch-show
      '(define-key notmuch-show-mode-map "`" 'notmuch-show-apply-tag-macro))

    (setq notmuch-show-tag-macro-alist
      (list
       '("m" "+notmuch::patch" "+notmuch::moreinfo" "-notmuch::needs-review")
       '("n" "+notmuch::patch" "+notmuch::needs-review" "-notmuch::pushed")
       '("o" "+notmuch::patch" "+notmuch::obsolete"
             "-notmuch::needs-review" "-notmuch::moreinfo")
       '("p" "-notmuch::pushed" "-notmuch::needs-review"
         "-notmuch::moreinfo" "+pending")
       '("P" "-pending" "-notmuch::needs-review" "-notmuch::moreinfo" "+notmuch::pushed")
       '("r" "-notmuch::patch" "+notmuch::review")
       '("s" "+notmuch::patch" "-notmuch::obsolete" "-notmuch::needs-review" "-notmuch::moreinfo" "+notmuch::stale")
       '("t" "+notmuch::patch" "-notmuch::needs-review" "+notmuch::trivial")
       '("w" "+notmuch::patch" "+notmuch::wip" "-notmuch::needs-review")))

    (defun notmuch-show-apply-tag-macro (key)
      (interactive "k")
      (let ((macro (assoc key notmuch-show-tag-macro-alist)))
        (apply 'notmuch-show-tag-message (cdr macro))))

## Restore reply-to-all key binding to 'r'

Starting from notmuch 0.12 the 'r' key is bound to reply-to-sender instead of
reply-to-all. Here's how to swap the reply to sender/all bindings in show mode:

        (define-key notmuch-show-mode-map "r" 'notmuch-show-reply)
        (define-key notmuch-show-mode-map "R" 'notmuch-show-reply-sender)

And in search mode:

        (define-key notmuch-search-mode-map "r" 'notmuch-search-reply-to-thread)
        (define-key notmuch-search-mode-map "R" 'notmuch-search-reply-to-thread-sender)


## How to do FCC/BCC...

The Emacs interface to notmuch will automatically add an `Fcc`
header to your outgoing mail so that any messages you send will also
be saved in your mail store. You can control where this copy of the
message is saved by setting the variable `notmuch-fcc-dirs` which defines the
subdirectory relative to the `database.path` setting from your
notmuch configuration in which to save the mail. Enter a directory
(without the maildir `/cur` ending which will be appended
automatically). Additional information can be found as usual using:

       M-x describe-variable notmuch-fcc-dirs

An additional variable that can affect FCC settings in some cases is
`message-directory`. Emacs message-mode uses this variable for
postponed messages.

To customize both variables at the same time, use the fancy command:

        M-x customize-apropos<RET>\(notmuch-fcc-dirs\)\|\(message-directory\)

This mechanism also allows you to select different folders to be
used for the outgoing mail depending on your selected `From`
address. Please see the documentation for the variable
`notmuch-fcc-dirs` in the customization window for how to arrange
this.

## How to customize `notmuch-saved-searches`

When starting notmuch, a list of saved searches and message counts is
displayed, replacing the older `notmuch-folders` command. The set of
saved searches displayed can be modified directly from the notmuch
interface (using the `[save]` button next to a previous search) or by
customising the variable `notmuch-saved-searches`.

An example setting for notmuch versions up to 0.17.x might be:

        (setq notmuch-saved-searches '(("inbox" . "tag:inbox")
                        ("unread" . "tag:inbox AND tag:unread")
                        ("notmuch" . "tag:inbox AND to:notmuchmail.org")))

Starting from notmuch 0.18 the variable changed. It is backwards
compatible so the above will still work but the new style will be used
if you use customize and there are some new features available. The above would become

        (setq notmuch-saved-searches '((:name "inbox" :query "tag:inbox")
                        (:name "unread" :query "tag:inbox AND tag:unread")
                        (:name "notmuch" :query "tag:inbox AND to:notmuchmail.org")))

The additional features are the possibility to set the search order
for the search, and the possibility to specify a different query for
displaying the count for the saved-search. For example

        (setq notmuch-saved-searches '((:name "inbox"
                                        :query "tag:inbox"
                                        :count-query "tag:inbox and tag:unread"
                                        :sort-order oldest-first)))

specifies a single saved search for inbox, but the number displayed by
the search will be the number of unread messages in the inbox, and the
sort order for this search will be oldest-first.

Of course, you can have any number of saved searches, each configured
with any supported search terms (see "notmuch help search-terms"), and
in the new style variable they can each have different count-queries
and sort orders.

Some users find it useful to add `and not tag:delete` to those
searches, as they use the `delete` tag to mark messages as
deleted. This causes messages that are marked as deleted to be removed
from the commonly used views of messages.  Use whatever seems most
useful to you.

## Viewing HTML messages with an external viewer

The Emacs client can generally display HTML messages inline using one of the
supported HTML renderers. This is controlled by the `mm-text-html-renderer`
variable.

Sometimes it may be necessary to display the message, or a single MIME part, in
an external browser. This can be done by `(notmuch-show-view-part)`, bound to
`. v` by default.

## msmtp, message mode and multiple accounts

As an alternative to running a mail server such as sendmail or postfix
just to send email, it is possible to use
[msmtp](http://msmtp.sourceforge.net/). This small application will
look like `/usr/bin/sendmail` to a MUA such as emacs message mode, but
will just forward the email to an external SMTP server. It's fairly
easy to set up and it supports several accounts for using different
SMTP servers. The msmtp pages have several examples.

A typical scenario is that you want to use the company SMTP server
for email coming from your company email address, and your personal
server for personal email.  If msmtp is passed the envelope address
on the command line (the -f/--from option) it will automatically
pick the matching account.  The only trick here seems to be getting
emacs to actually pass the envelope from.  There are a number of
overlapping configuration variables that control this, and it's a
little confusion, but setting these three works for me:

 - `mail-specify-envelope-from`: `t`

 - `message-sendmail-envelope-from`: `header`

 - `mail-envelope-from`: `header`

With that in place, you need a `.msmtprc` with the accounts configured
for the domains you want to send out using specific SMTP servers and
the rest will go to the default account.

## <span id="address_completion">Address completion when composing</span>

There are currently three solutions to this:

### bbdb

[bbdb](http://bbdb.sourceforge.net) is a contact database for emacs
that works quite nicely together with message mode, including
address autocompletion.

### notmuch database as an address book

You can also use the notmuch database as a mail address book itself.
To do this you need a command line tool that outputs likely address
candidates based on a search string.  There are currently four
available:

  * The python tool `notmuch_address.py` (`git clone
    http://commonmeasure.org/~jkr/git/notmuch_addresses.git`) (slower, but
    no compilation required so good for testing the setup)

  * The C-based [notmuch-addrlookup](https://github.com/aperezdc/notmuch-addrlookup-c) by [Adrian Perez](http://perezdecastro.org/), which is faster but needs to be compiled.

        git clone https://github.com/aperezdc/notmuch-addrlookup-c
        cd notmuch-addrlookup-c
        make

  * The vala-based
    [addrlookup](http://github.com/spaetz/vala-notmuch) The addrlookup binary needs to be compiled.
    Grab
    `http://github.com/spaetz/vala-notmuch/raw/static-sources/src/addrlookup.c`
    and build it with:

            cc -o addrlookup addrlookup.c `pkg-config --cflags --libs gobject-2.0` -lnotmuch

  * Shell/fgrep/perl combination [nottoomuch-addresses.sh](https://github.com/domo141/nottoomuch/blob/master/nottoomuch-addresses.rst).
    This tools maintains it's own address "database" gathered from email
    files notmuch knows and search from that "database" is done by `fgrep(1)`.

  * python/sqlite combination [notmuch-abook](https://github.com/guyzmo/notmuch-abook/)
    This tools also maintains an address database in sqlite after harvesting
    from notmuch.  It also includes a vim plugin.

You can perform tab-completion using any of these programs.
Just add the following to your [notmuch init file](/notmuch-emacs#notmuch_init_file):

        (require 'notmuch-address)
        (setq notmuch-address-command "/path/to/address_fetching_program")
        (notmuch-address-message-insinuate)

### Google Contacts

[GooBook](http://code.google.com/p/goobook/) is a command-line tool for
accessing Google Contacts. Install and set it up according to its documentation.

To use GooBook with notmuch, use this wrapper script and set it up like the
programs above.

        #!/bin/sh
        goobook query "$*" | sed 's/\(.*\)\t\(.*\)\t.*/\2 \<\1\>/' | sed '/^$/d'

You can add the sender of a message to Google Contacts by piping the message
(`notmuch-show-pipe-message`) to `goobook add`.

### Akonadi

        git clone https://github.com/mmehnert/akonadimailsearch

Install the development packages for kdepim on your system.
Enter the cloned repository and create a build directory:

        mkdir build
        cd build
        cmake ..; make;

You will find the akonadimailsearch binary in the build/src directory. Copy it to ~/bin .

You can now add the following settings to your
[notmuch init file](/notmuch-emacs#notmuch_init_file):

        (require 'notmuch-address)
        (setq notmuch-address-command "~/bin/akonadimailsearch")
        (notmuch-address-message-insinuate)

### Completion selection with helm

An address query might return multiple possible matches from which you
will have to select one. To ease this task, several different
frameworks in emacs support completion selection. One of them is
[helm](https://github.com/emacs-helm/helm). The following snippet
improves the out-of-the-box support for helm in notmuch as it enables
the required-match option and also does not ignore the first returned
address.

        (setq notmuch-address-selection-function
          (lambda (prompt collection initial-input)
            (completing-read prompt (cons initial-input collection) nil t nil 'notmuch-address-history)))


## How to sign/encrypt messages with gpg

Messages can by signed using gpg by invoking
`M-x mml-secure-sign-pgpmime` (or `M-x mml-secure-encrypt-pgpmime`).
These functions are available via the standard `message-mode` keybindings
`C-c C-m s p` and `C-c C-m c p`. To sign outgoing mail by default, use the
`message-setup-hook` in your `.emacs` file:

        ;; Sign messages by default.
        (add-hook 'message-setup-hook 'mml-secure-sign-pgpmime)

This inserts the required `<#part sign=pgpmime>` into the beginning
of the mail text body and will be converted into a pgp signature
when sending (so one can just manually delete that line if signing
is not required).

Alternatively, you may prefer to use `mml-secure-message-sign-pgpmime` instead
of `mml-secure-sign-pgpmime` to sign the whole message instead of just one
part.

### Troubleshooting message-mode gpg support

- If you have trouble with expired subkeys, you may have encountered
  emacs bug #7931.  This is fixed in git commit 301ea744c on
  2011-02-02.  Note that if you have the Debian package easypg
  installed, it will shadow the fixed version of easypg included with
  emacs.

- If you wish `mml-secure-encrypt` to encrypt also for the sender, then
  `M-x customize-variable mml2015-encrypt-to-self` might suit your need.

## Reading and verifying encrypted and signed messages

Encrypted and signed mime messages can be read and verified with:

        (notmuch-crypto-process-mime t)

Decrypting or verifying inline pgp messages can be done by selecting
an the inline pgp area and and using:

        M-x epa-decrypt-region RET

## Multiple identities using gnus-alias

[gnus-alias](http://www.emacswiki.org/emacs/GnusAlias) allows you to
define multiple identities when using `message-mode`. You can specify
the from address, organization, extra headers (including *Bcc*), extra
body text, and signature for each identity. Identities are chosen
based on a set of rules. When you are in message mode, you can switch
identities using gnus-alias.

### Installation

- put `gnus-alias.el` on your load Emacs-Lisp load path (add new directory
  to load path by writing `(add-to-list 'load-path "/some/load/path")` into
  your `.emacs`.

- Add the following to your `.emacs`

        (autoload 'gnus-alias-determine-identity "gnus-alias" "" t)
        (add-hook 'message-setup-hook 'gnus-alias-determine-identity)

Looking into `gnus-alias.el` gives a bit more information...

### Example Configuration

Here is an example configuration.

        ;; Define two identities, "home" and "work"
        (setq gnus-alias-identity-alist
              '(("home"
                 nil ;; Does not refer to any other identity
                 "John Doe <jdoe@example.net>" ;; Sender address
                 nil ;; No organization header
                 nil ;; No extra headers
                 nil ;; No extra body text
                 "~/.signature")
                ("work"
                 nil
                 "John Doe <john.doe@example.com>"
                 "Example Corp."
                 (("Bcc" . "john.doe@example.com"))
                 nil
                 "~/.signature.work")))
        ;; Use "home" identity by default
        (setq gnus-alias-default-identity "home")
        ;; Define rules to match work identity
        (setq gnus-alias-identity-rules)
              '(("work" ("any" "john.doe@\\(example\\.com\\|help\\.example.com\\)" both) "work"))
        ;; Determine identity when message-mode loads
        (add-hook 'message-setup-hook 'gnus-alias-determine-identity)

When `gnus-alias` has been loaded (using autoload, require, *M-x load-library*
or *M-x load-file* (load-file takes file path -- therefore it can be used
without any `.emacs` changes)) the following commands can be used to get(/set)
more information (some of these have "extensive documentation"):

        M-x describe-variable RET gnus-alias-identity-alist
        M-x describe-variable RET gnus-alias-identity-rules
        M-x describe-variable RET gnus-alias-default-identity

        M-x customize-group RET gnus-alias RET
          or
        M-x gnus-alias-customize RET

The last two do the same thing.

See also the **Usage:** section in `gnus-alias.el`.

## Resending (or bouncing) messages

Add the following to your [notmuch init file](/notmuch-emacs#notmuch_init_file) to be able
to resend the current message in show mode.

        (define-key notmuch-show-mode-map "b"
          (lambda (&optional address)
            "Bounce the current message."
            (interactive "sBounce To: ")
            (notmuch-show-view-raw-message)
            (message-resend address)))

## `notmuch-hello` refresh status message

Add the following to your [notmuch init file](/notmuch-emacs#notmuch_init_file) to get a
status message about the change in the number of messages in the mail store
when refreshing the `notmuch-hello` buffer.

        (defvar notmuch-hello-refresh-count 0)

        (defun notmuch-hello-refresh-status-message ()
          (unless no-display
            (let* ((new-count
                    (string-to-number
                     (car (process-lines notmuch-command "count"))))
                   (diff-count (- new-count notmuch-hello-refresh-count)))
              (cond
               ((= notmuch-hello-refresh-count 0)
                (message "You have %s messages."
                         (notmuch-hello-nice-number new-count)))
               ((> diff-count 0)
                (message "You have %s more messages since last refresh."
                         (notmuch-hello-nice-number diff-count)))
               ((< diff-count 0)
                (message "You have %s fewer messages since last refresh."
                         (notmuch-hello-nice-number (- diff-count)))))
              (setq notmuch-hello-refresh-count new-count))))

        (add-hook 'notmuch-hello-refresh-hook 'notmuch-hello-refresh-status-message)

## Replacing tabs with spaces in subject and header

Mailman mailing list software rewrites and rewraps long message subjects in
a way that causes TABs to appear in the middle of the subject and header
lines. Add this to your [notmuch init file](/notmuch-emacs#notmuch_init_file) to replace
tabs with spaces in subject lines:

        (defun notmuch-show-subject-tabs-to-spaces ()
          "Replace tabs with spaces in subject line."
          (goto-char (point-min))
          (when (re-search-forward "^Subject:" nil t)
            (while (re-search-forward "\t" (line-end-position) t)
              (replace-match " " nil nil))))

        (add-hook 'notmuch-show-markup-headers-hook 'notmuch-show-subject-tabs-to-spaces)

And in header lines (this will only work with the yet to be released
notmuch version 0.15):

        (defun notmuch-show-header-tabs-to-spaces ()
          "Replace tabs with spaces in header line."
          (setq header-line-format
                (notmuch-show-strip-re
                 (replace-regexp-in-string "\t" " " (notmuch-show-get-subject)))))

        (add-hook 'notmuch-show-hook 'notmuch-show-header-tabs-to-spaces)

## Hiding unread messages in notmuch-show

I like to have an inbox saved search, but only show unread messages when they
view a thread. This takes two steps:

1. Apply
[this patch from Mark Walters](http://notmuchmail.org/pipermail/notmuch/2012/010817.html)
to add the `notmuch-show-filter-thread` function.
1. Add the following hook to your emacs configuration:

        (defun expand-only-unread-hook () (interactive)
          (let ((unread nil)
                (open (notmuch-show-get-message-ids-for-open-messages)))
            (notmuch-show-mapc (lambda ()
                                 (when (member "unread" (notmuch-show-get-tags))
                                   (setq unread t))))
            (when unread
              (let ((notmuch-show-hook (remove 'expand-only-unread-hook notmuch-show-hook)))
                (notmuch-show-filter-thread "tag:unread")))))

        (add-hook 'notmuch-show-hook 'expand-only-unread-hook)

## Changing the color of a saved search based on some other search

I like to have a saved search for my inbox, but have it change color when there
are thread with unread messages in the inbox. I accomplish this with the
following code in my emacs config:

        (defun color-inbox-if-unread () (interactive)
          (save-excursion
            (goto-char (point-min))
            (let ((cnt (car (process-lines "notmuch" "count" "tag:inbox and tag:unread"))))
              (when (> (string-to-number cnt) 0)
                (save-excursion
                  (when (search-forward "inbox" (point-max) t)
                    (let* ((overlays (overlays-in (match-beginning 0) (match-end 0)))
                           (overlay (car overlays)))
                      (when overlay
                        (overlay-put overlay 'face '((:inherit bold) (:foreground "green")))))))))))
        (add-hook 'notmuch-hello-refresh-hook 'color-inbox-if-unread)

## Linking to notmuch messages and threads from the Circe IRC client

[Circe](https://github.com/jorgenschaefer/circe/wiki) is an IRC client for emacs.
To have clickable buttons for notmuch messages and threads, add the following to
`lui-buttons-list` (using, e.g. M-x customize-variable)

    ("\\(?:id\\|mid\\|thread\\):[0-9A-Za-z][0-9A-Za-z.@-]*" 0 notmuch-show 0)

If you have notmuch-pick installed, it works fine for this as well.

## Linking to notmuch messages from org-mode

Support for linking to notmuch messages is distributed with org-mode,
but as a contrib file, so you might have to work a bit to load it.

In Debian and derivatives,

    (add-to-list 'load-path "/usr/share/org-mode/lisp")

Then

    (require 'org-notmuch)

In general it is nice to have a key for org-links (not just for notmuch). For example

    (define-key global-map "\C-cl" 'org-store-link)

## Viewing diffs in notmuch

The following code allows you to view an inline patch in diff-mode
directly from notmuch. This means that normal diff-mode commands like
refine, next hunk etc all work.

    (defun my-notmuch-show-view-as-patch ()
      "View the the current message as a patch."
      (interactive)
      (let* ((id (notmuch-show-get-message-id))
             (subject (concat "Subject: " (notmuch-show-get-subject) "\n"))
             (diff-default-read-only t)
             (buf (get-buffer-create (concat "*notmuch-patch-" id "*")))
             (map (make-sparse-keymap)))
        (define-key map "q" 'notmuch-kill-this-buffer)
        (switch-to-buffer buf)
        (let ((inhibit-read-only t))
          (erase-buffer)
          (insert subject)
          (insert (notmuch-get-bodypart-internal id 1 nil)))
        (set-buffer-modified-p nil)
        (diff-mode)
        (lexical-let ((new-ro-bind (cons 'buffer-read-only map)))
                     (add-to-list 'minor-mode-overriding-map-alist new-ro-bind))
        (goto-char (point-min))))

and then this function needs to bound into the keymap with something like

    (define-key 'notmuch-show-mode-map "D" 'my-notmuch-show-view-as-patch)

## Interfacing with Patchwork

[Patchwork](http://jk.ozlabs.org/projects/patchwork/) is a web-based system for
tracking patches sent to a mailing list. While the Notmuch project doesn't use
it, many other open source projects do. Having an easy way to get from a patch
email in your favorite mail client to the web page of the patch in the Patchwork
instance is a cool thing to have. Here's how to abuse the notmuch stash feature
to achieve this. (Don't know stash? See `notmuch-show-stash-mlarchive-link`,
bound to `c l` in `notmuch-show`.)

The trick needed is turning the email Message-ID into a unique Patchwork ID
assigned by Patchwork. We'll use the `pwclient` command-line tool to achieve
this. You'll first need to get that working and configured for the Patchwork
instance you're using. That part is beyond this tip here; please refer to
Patchwork documentation.

Check your configuration on the command-line, for example:

    /path/to/pwclient -p <the-project> -n 5 -f "%{id}"

Note that the -f format argument may require a reasonably new version of the
client. Once you have the above working, you can `M-x customize-variable RET
notmuch-show-stash-mlarchive-link-alist RET`.

Add a new entry with "Function returning the URL:" set to:

    (lambda (message-id)
      (concat "http://patchwork.example.com/patch/"
              (nth 0
                   (process-lines "/path/to/pwclient" "search"
                                  "-p" "the-project"
                                  "-m" (concat "<" message-id ">")
                                  "-n" "1"
                                  "-f" "%{id}"))))

Replacing `http://patchwork.example.com/patch/`, `/path/to/pwclient`, and
`the-project` appropiately. You should now be able to stash the Patchwork URL
using `c l`.

Going further, if the patch has been committed, you can get the commit hash with
this:

    (lambda (message-id)
      (nth 0
           (process-lines "/path/to/pwclient" "search"
                          "-p" "the-project"
                          "-m" (concat "<" message-id ">")
                          "-n" "1"
                          "-f" "%{commit_ref}")))

And finally, if the project has a web interface to its source repository, you
can turn the commit hash into a URL pointing there, for example:

    (lambda (message-id)
      (concat "http://cgit.example.com/the-project/commit/?id="
              (nth 0
                   (process-lines "/path/to/pwclient" "search"
                                  "-p" "the-project"
                                  "-m" (concat "<" message-id ">")
                                  "-n" "1"
                                  "-f" "%{commit_ref}"))))