aboutsummaryrefslogtreecommitdiff
path: root/piem.el
blob: 0b3d7448a659085c7003a00c139ed7a10fe99005 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
;;; piem.el --- Emacs tools for working with public-inbox  -*- lexical-binding: t; -*-

;; Copyright (C) 2020-2021  all contributors <piem@inbox.kyleam.com>

;; Author: Kyle Meyer <kyle@kyleam.com>
;; Keywords: vc, tools
;; Version: 0.2.0
;; Package-Requires: ((emacs "26.3") (transient "0.3.0"))
;; Homepage: https://git.kyleam.com/piem/about/

;; This program is free software; you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation, either version 3 of the License, or
;; (at your option) any later version.

;; This program is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;; GNU General Public License for more details.

;; You should have received a copy of the GNU General Public License
;; along with this program.  If not, see <https://www.gnu.org/licenses/>.

;;; Commentary:

;; This library provides functionality for working with public-inbox
;; archives [1] within Emacs (e.g., applying a patch series to the
;; associated Git repository or downloading an mbox for the thread and
;; injecting it into a local Maildir directory).  The user option
;; `piem-inboxes' defines a set of public-inbox archives.  For most
;; the functions here to do something useful, the current buffer needs
;; to be linked to an inbox in that list, which requires enabling the
;; minor mode provided by at least one integration library (such as
;; `piem-gnus', `piem-eww', or `piem-notmuch').
;;
;; [1] https://public-inbox.org/README

;;; Code:

(require 'browse-url)
(require 'cl-lib)
(require 'mail-extr)
(require 'message)
(require 'mm-decode)
(require 'piem-maildir)
(require 'rfc2047)
(require 'subr-x)
(require 'transient)
(require 'url)
(require 'url-handlers)
(require 'url-http)



;;;; Options

(defgroup piem ()
  "Emacs tools for working with public-inbox archives."
  :link '(info-link "(piem)Top")
  :group 'tools)

;; TODO: These intentionally follow public-inbox's configuration
;; names.  Eventually reading values from there as well should be
;; supported.
;;
;; TODO: Decide how to deal with inboxes that map to more than one
;; coderepos.  This is important to support for people that want to
;; use a catchall inbox for small projects which they don't think
;; (yet) need a dedicated address.
(defcustom piem-inboxes nil
  "List of public-inbox-archived projects.

Elements have the form (NAME . INFO), where INFO is a property
list that supports the following properties:

  :address
  :listid
      The email address and List-ID for the inbox.
  :coderepo
      Local path of the code repository associated with the inbox.
  :url
      A URL hosting HTTPS archives.  This value must end with a slash.
  :maildir
      A Maildir directory to inject messages into.

Here's an example for the public-inbox project itself:

    (\"public-inbox\"
     :coderepo \"~/src/public-inbox/\"
     :address \"meta@public-inbox.org\"
     :listid \"meta.public-inbox.org\"
     :url \"https://public-inbox.org/meta/\"
     :maildir \"~/.local/share/mail/.lists.mail.public-inbox\")"
  :type '(alist :key-type string
                :value-type
                (plist :value-type string)))

(defcustom piem-get-inbox-functions nil
  "Functions tried to get the inbox of the current buffer.
Each function should accept no arguments and return the name of
the inbox associated with the current buffer or nil."
  :type 'hook)

(defcustom piem-get-mid-functions nil
  "Functions tried to get the message ID of the current buffer.
Each function should accept no arguments and return the
message ID associated with the current buffer or nil."
  :type 'hook)

(defcustom piem-mid-to-thread-functions nil
  "Functions tried to create an mbox from a message ID.
Each function should accept one argument, the message ID.  If the
function knows how to create an mbox for the message ID, it
should return a function that takes no arguments and inserts the
mbox's contents (in mboxrd format) in the current buffer."
  :type 'hook)

(defcustom piem-am-ready-mbox-functions nil
  "Functions tried to get an mbox to be fed to `git am'.
The functions are called with no arguments.  If a function knows
how to create an mbox, it should return a function that takes no
arguments and inserts the mbox's contents in the current buffer.
The return value can also be (FUNCTION . FORMAT), where FORMAT is
either \"mbox\" or \"mboxrd\" and maps to the --patch-format
value passed to `git am'.  If unspecified, \"mboxrd\" is used."
  :type 'hook)

(defcustom piem-add-message-id-header nil
  "Whether to add Message-Id header to non-mail patches.
If this value is non-nil and a patch returned by a function in
`piem-am-ready-mbox-functions' looks like a patch that was
attached rather than sent inline, add a Message-Id header with
the return value of `piem-mid'."
  :type 'boolean)

(defcustom piem-git-executable
  (or (and (boundp 'magit-git-executable) magit-git-executable)
      "git")
  "Which git executable to use."
  :type 'string)

(defcustom piem-use-magit t
  "Whether to use Magit for some user-facing operations."
  :type 'boolean)

(defcustom piem-default-branch-function
  #'piem-name-branch-who-what-v
  "Function that generates the default branch on completion.

The function is called with one argument, a plist that contains
the following information about the patch series:

  :date
  :from
  :subject
      The date, sender, and subject of the cover letter, if any, or of
      the first patch otherwise.
  :base-commit
      The reported base commit of the patch, if any."
  :type 'function)

(defcustom piem-am-create-worktree nil
  "Whether to create a dedicated worktree for applying patches."
  :type 'boolean)

(defcustom piem-am-read-worktree-function #'piem-am-read-worktree
  "Function that reads a to-be-created worktree from the user.
This function is called with two arguments, the directory of the
code repository that the worktree will be created from and the
name of the branch that will be created.  The branch may be nil
if the caller requested a detached HEAD."
  :type 'function)

(defcustom piem-maildir-directory nil
  "Default directory to inject public-inbox threads into.

If non-nil, this must be an existing Maildir directory.  This can be
overriden on a per-list basis by using the \":maildir\" keyword in
`piem-inboxes'."
  :type 'string)

(defcustom piem-mail-injection-skipif-predicate nil
  "Predicate to decide whether to skip injecting a message.

The function is called with the message ID (no surrounding
brackets) within a buffer that is narrowed to the message.  The
function does not need to worry about saving point.  A non-nil
return value signals that `piem-inject-thread-into-maildir'
should skip the message.

Notmuch users can use `piem-notmuch-known-mid-p' as the predicate
to skip messages that are already in the Notmuch database."
  :type 'function)

(defcustom piem-after-mail-injection-functions nil
  "Functions called after writing messages to `piem-maildir-directory'.
Functions should accept one argument, the message ID given to
`piem-inject-thread-into-maildir'."
  :type 'hook)

(defcustom piem-browse-url-browser-function nil
  "Overriding value for `browse-url-browser-function'.

public-inbox's HTTP interface is well suited for browsers like
w3m and EWW, allowing you to stay in Emacs rather than launch an
external browser.  However, assuming you have `browse-url'
configured to usually go through an external browser, sending
public-inbox URLs through, say, EWW would require you to
configure `browse-url-browser-function' with a regular expression
for each inbox URL that you want to be handled by
`eww-browse-url'.

Instead, you can simply set this option to `eww-browse-url' (or
anything else `browse-url-browser-function' accepts), and piem
will use it when calling `browse-url'.

When this option is nil, piem calls `browse-url' without
overriding the value of `browse-url-browser-function'."
  :type (append
         '(choice
           (const :tag "Don't override `browse-url-browser-function'" nil))
         (cdr (get 'browse-url-browser-function 'custom-type))))


;;;; Subprocess handling

(defvar piem-process-mode-font-lock-keywords
  `((,(rx line-start
          ";;; " (or "process" "directory" "time")
          ":" (one-or-more not-newline)
          line-end)
      (0 font-lock-comment-face t))
    (,(rx line-start
          "Process " (one-or-more not-newline) " finished"
          line-end)
     (0 font-lock-comment-face))))

(defconst piem-process-output-buffer "*piem-process-output*")

(define-derived-mode piem-process-mode nil "piem-process"
  "Major mode for displaying processes created by piem."
  :group 'piem
  (setq buffer-read-only t)
  (setq-local window-point-insertion-type t)
  (setq-local font-lock-defaults
              '(piem-process-mode-font-lock-keywords)))

(define-error 'piem-process-error "piem process error")

(defvar-local piem--buffer-process nil)

(defun piem--process-go (dir program program-args fn)
  (setq dir (or dir default-directory))
  (let ((buffer (get-buffer-create piem-process-output-buffer)))
    (with-current-buffer buffer
      (when (and piem--buffer-process
                 (process-live-p piem--buffer-process))
        (user-error "Buffer %s already has an active process: %s"
                    (current-buffer) piem--buffer-process))
      (unless (derived-mode-p 'piem-process-mode)
        (piem-process-mode))
      (setq default-directory (file-name-as-directory dir))
      (goto-char (point-max))
      (display-buffer buffer)
      (let ((inhibit-read-only t))
        (insert (format "
%s
;;; process: %S
;;; directory:  %s
;;; time: %s
"
                        (char-to-string 12) ; form feed
                        (cons program program-args)
                        default-directory
                        (format-time-string "%FT%T%z")))
        (funcall fn)))))

(defun piem-process-start (dir program &rest program-args)
  (setq program-args (remq nil program-args))
  (piem--process-go
   dir program program-args
   (lambda ()
     (setq piem--buffer-process
          (apply #'start-process
                 (file-name-nondirectory program)
                 (current-buffer)
                 program program-args)))))

(defun piem-process-call (dir program &rest program-args)
  (setq program-args (remq nil program-args))
  (piem--process-go
   dir program program-args
   (lambda ()
     (unless (= 0 (apply #'call-process program nil t nil program-args))
       (signal 'piem-process-error
               (list (format "%s call in %s failed"
                             program default-directory)))))))

(defun piem-process-call-with-buffer-input
    (dir buffer program &rest program-args)
  (setq program-args (remq nil program-args))
  (piem--process-go
   dir program program-args
   (lambda ()
     (let ((outdir default-directory)
           (outbuf (current-buffer)))
       (with-current-buffer buffer
         (let ((default-directory outdir))
           (unless (= 0 (apply #'call-process-region nil nil
                               program nil outbuf nil program-args))
             (signal 'piem-process-error
                     (list (format "%s call in %s failed"
                                   program default-directory))))))))))


;;;; Extractors

(defun piem--ensure-trailing-slash (s)
  (if (string-suffix-p "/" s) s (concat s "/")))

(defun piem-message-link-re (url &optional mid)
  "Return a regular expression matching a public-inbox url.
URL should be the top-level url for the inbox.  If MID is
non-nil, make the match specific for that message."
  (rx-to-string
   `(and ,(piem--ensure-trailing-slash url)
         (group ,(or (and mid (piem-escape-mid mid))
                     '(one-or-more (not (any "/" "\n")))))
         "/" (group (zero-or-one
                     (or "raw"
                         "t.mbox.gz"
                         (and (or "t" "T") "/#"
                              (one-or-more (not (any "/" "\n")))))))
         string-end)))

(defun piem--message-fetch-decoded-fields (headers)
  (save-excursion
    (save-restriction
      (message-narrow-to-head)
      (mapcar (lambda (header)
                (when-let ((val (message-fetch-field header)))
                  (rfc2047-decode-string val)))
              headers))))

(defun piem-inbox-by-header-match ()
  "Return inbox based on matching message headers.
This should be called from a buffer containing a message and is
intended to be used by libraries implementing a function for
`piem-get-mid-functions'."
  (pcase-let ((`(,listid ,to ,cc)
               (piem--message-fetch-decoded-fields '("list-id" "to" "cc"))))
    (catch 'hit
      (dolist (inbox piem-inboxes)
        (let* ((info (cdr inbox))
               (p-listid (plist-get info :listid)))
          (when (and listid
                     p-listid
                     (string-match-p (concat "<" (regexp-quote p-listid) ">")
                                     listid))
            (throw 'hit (car inbox)))
          (when-let ((addr (plist-get info :address))
                     (to (mapconcat #'identity (list to cc)
                                    " ")))
            (when (string-match-p (regexp-quote addr) to)
              (throw 'hit (car inbox)))))))))

(defun piem-inbox ()
  "Return the current buffer's inbox."
  (run-hook-with-args-until-success 'piem-get-inbox-functions))

(defun piem-inbox-get (key &optional inbox)
  "Get info KEY for INBOX's entry in `piem-inboxes'.
If INBOX is nil, use the inbox returned by `piem-inbox'."
  (when-let ((p (or inbox (piem-inbox))))
    (plist-get (cdr (assoc p piem-inboxes)) key)))

(defun piem-inbox-coderepo (&optional inbox)
  "Return the code repository of current buffer's inbox."
  (when-let ((repo (piem-inbox-get :coderepo inbox)))
    (expand-file-name repo)))

(defun piem-inbox-maildir-directory (&optional inbox)
  "Return the maildir for INBOX's entry in `piem-inboxes'.

If INBOX is nil, use the inbox returned by `piem-inbox'.  If the
INBOX doesn't have a maildir configured, return the value of
`piem-maildir-directory'."
  (or (piem-inbox-get :maildir inbox)
      piem-maildir-directory))

(defun piem-inbox-by-url-match (url)
  "Return inbox based on matching URL against `:url'."
  (setq url (piem--ensure-trailing-slash url))
  (catch 'hit
    (dolist (inbox piem-inboxes)
      (when-let ((info (cdr inbox))
                 (p-url (plist-get info :url)))
        (setq p-url (piem--ensure-trailing-slash p-url))
        (when (string-match-p (regexp-quote p-url) url)
          (throw 'hit (car inbox)))))))

(defun piem-inbox-coderepo-maybe-read ()
  "Like `piem-inbox-coderepo', but fall back to reading the repo."
  (let ((inbox
         (or (piem-inbox-coderepo)
             (and (bound-and-true-p projectile-known-projects)
                  (expand-file-name
                   (completing-read
                    "Project: "
                    projectile-known-projects nil t nil nil
                    (when-let ((current (and (fboundp 'projectile-project-root)
                                             (projectile-project-root))))
                      (abbreviate-file-name current)))))
             (and (bound-and-true-p project-list-file)
                  (file-exists-p project-list-file)
                  (fboundp 'project-prompt-project-dir)
                  (expand-file-name
                   (project-prompt-project-dir)))
             (and piem-use-magit
                  (fboundp 'magit-read-repository)
                  (magit-read-repository))
             (read-directory-name "Git repository: "))))
    (if (equal inbox "")
        (user-error "No inbox specified")
      inbox)))

(defun piem-mid ()
  "Return the current buffer's message ID."
  (run-hook-with-args-until-success 'piem-get-mid-functions))

(defun piem--insert-message-id-header (mid)
  ;; Be strict about case because this is coming from
  ;; git-format-patch.
  (let ((case-fold-search nil))
    (while (re-search-forward
            (rx line-start
                "From " (>= 40 hex-digit) " Mon Sep 17 00:00:00 2001"
                line-end)
            nil t)
      (catch 'has-message-id
        (let ((header-count 0))
          (while (and (= (forward-line) 0)
                      (not (looking-at-p
                            (rx line-start (zero-or-one space) line-end))))
            (cond
             ((looking-at-p
               (rx line-start
                   "Message-Id: <" (one-or-more not-newline) ">"
                   line-end))
              (throw 'has-message-id nil))
             ((looking-at-p
               (rx line-start (or "From" "Date" "Subject") ": "
                   not-newline))
              (cl-incf header-count))))
          (when (= header-count 3)
            ;; Found all the expected headers before hitting a
            ;; blank line.  Assume we're in a header.
            (insert (format "Message-Id: <%s>\n" mid))))))))

(defun piem-am-ready-mbox ()
  "Generate a buffer containing an am-ready mbox.
The return value is (BUFFER . FORMAT), where FORMAT is either
\"mbox\" or \"mboxrd\".  Callers are responsible for killing the
buffer."
  (when-let ((res (run-hook-with-args-until-success
                   'piem-am-ready-mbox-functions)))
    (pcase-let ((buffer (generate-new-buffer " *piem am-ready mbox*"))
                (`(,fn . ,format)
                 (if (member (cdr-safe res) '("mbox" "mboxrd"))
                     res
                   (cons res "mboxrd")))
                (mid (and piem-add-message-id-header (piem-mid)))
                (has-content nil))
      (with-current-buffer buffer
        (funcall fn)
        (setq has-content (< 1 (point-max)))
        (when (and has-content mid)
          (goto-char (point-min))
          (piem--insert-message-id-header mid)))
      (if has-content
          (cons buffer format)
        (kill-buffer buffer)
        nil))))


;;;; Link handling

(defconst piem--unreserved-chars
  (append url-unreserved-chars
          ;; These extra characters follow what's used by
          ;; public-inbox's mid_escape().
          (list ?! ?$ ?& ?' ?\( ?\) ?* ?+ ?, ?= ?: ?\; ?@)))

(defun piem-escape-mid (mid)
  "Escape MID for use in path part of a public-inbox URL."
  (url-hexify-string mid piem--unreserved-chars))

(defun piem-mid-url (mid &optional inbox)
  "Return a public-inbox URL for MID.
The URL is determined by INBOX's entry in `piem-inboxes'.  If
INBOX is nil, use the inbox returned by `piem-inbox'."
  (concat
   (piem--ensure-trailing-slash
    (or (piem-inbox-get :url inbox)
        (user-error "Couldn't find URL for %s"
                    (or inbox "current buffer"))))
   (piem-escape-mid mid)))

;;;###autoload
(defun piem-copy-mid-url (&optional browse)
  "Copy public-inbox URL for the current buffer's message.
With prefix argument BROWSE, call `browse-url' on the URL
afterwards.  If `piem-browse-url-browser-function' is non-nil, it
is used as the value of `browse-url-browser-function'."
  (interactive "P")
  (let ((url (piem-mid-url
              (or (piem-mid)
                  (user-error "No message ID found for the current buffer"))
              (piem-inbox))))
    (prog1
        (kill-new (message "%s" url))
      (when browse
        (let ((browse-url-browser-function
               (or piem-browse-url-browser-function
                   browse-url-browser-function)))
          (browse-url url))))))


;;;; Download helpers

(defvar piem--has-gunzip)
(defun piem-gunzip-buffer ()
  (unless (if (boundp 'piem--has-gunzip)
              piem--has-gunzip
            (setq piem--has-gunzip (executable-find "gunzip")))
    (user-error "gunzip executable not found"))
  (goto-char (point-min))
  (unless (= 0 (call-process-region nil nil "gunzip" nil t))
    (error "Decompressing buffer failed"))
  (delete-region (point) (point-max))
  (goto-char (point-min)))

(defmacro piem-with-url-contents (url &rest body)
  "Insert URL contents literally into temporary buffer and evaluate BODY."
  (declare (indent 1) (debug t))
  (let ((u (cl-gensym "url")))
    `(with-temp-buffer
       (set-buffer-multibyte nil)
       ;; This mostly copies `url-insert-file-contents', but it embeds
       ;; `url-http--insert-file-helper' and uses `url-insert' rather
       ;; than `url-insert-buffer-contents' to insert the contents
       ;; literally.
       (let* ((,u ,url)
              (buffer (url-retrieve-synchronously ,u)))
         (unless buffer (signal 'file-error (list ,u "No Data")))
         ;; This error handling follows what's in
         ;; `url-http--insert-file-helper'.
         (with-current-buffer buffer
           (when (bound-and-true-p url-http-response-status)
             (unless (or (and (>= url-http-response-status 200)
                              (< url-http-response-status 300))
                         (= url-http-response-status 304))
               (let ((desc (nth 2 (assq url-http-response-status url-http-codes))))
                 (kill-buffer buffer)
                 (signal 'file-error (list ,u desc))))))
         (url-insert buffer))
       (goto-char (point-min))
       ,@body)))


;;;; Maildir injection

(defun piem--write-mbox-to-maildir (maildir-directory)
  (let ((n-added 0)
        (n-skipped 0))
    (while (and (not (eobp))
                (re-search-forward "^From mboxrd@z" nil t))
      (let* ((beg (line-beginning-position 2))
             (end (or (and (re-search-forward "^From mboxrd@z" nil t)
                           (progn (goto-char (line-beginning-position 0))
                                  (point-marker)))
                      (point-max-marker)))
             (basename (piem-maildir-make-uniq-maildir-id))
             (tmpfile (concat maildir-directory "/tmp/" basename)))
        (goto-char beg)
        (if (and (functionp piem-mail-injection-skipif-predicate)
                 (save-excursion
                   (save-restriction
                     (narrow-to-region beg end)
                     (funcall piem-mail-injection-skipif-predicate
                              (replace-regexp-in-string
                               "\\`<\\(.*\\)>\\'" "\\1"
                               (or (save-restriction
                                     (save-excursion
                                       (message-narrow-to-head-1)
                                       (message-fetch-field "message-id" t)))
                                   (error "Message lacks message-ID")))))))
            (cl-incf n-skipped)
          (let ((case-fold-search nil))
            (while (re-search-forward
                    (rx line-start ">" (group (zero-or-more ">") "From "))
                    end t)
              (replace-match "\\1" t)))
          (write-region beg end tmpfile nil nil nil 'excl)
          (piem-maildir-move-tmp-to-new maildir-directory
                                        basename)
          (delete-file tmpfile)
          (cl-incf n-added))
        (goto-char end)))
    (cons n-added n-skipped)))

;;;###autoload
(defun piem-inject-thread-into-maildir (mid &optional message-only)
  "Inject thread containing MID into `piem-inbox-maildir-directory'.

If prefix argument MESSAGE-ONLY is non-nil, inject just the
message for MID, not the entire thread.

This function depends on :url being configured for entries in
`piem-inboxes'."
  (interactive
   (list (or (piem-mid)
             (user-error "No message ID found for the current buffer"))
         current-prefix-arg))
  (let ((maildir-directory (piem-inbox-maildir-directory)))
    (cond
     ((not maildir-directory)
      (user-error "No directory returned by `piem-inbox-maildir-directory'"))
     ((not (piem-maildir-dir-is-maildir-p maildir-directory))
      (user-error
       "Does not look like a Maildir directory: %s" maildir-directory)))
    (let ((url (concat (piem-mid-url mid)
                       (if message-only "/raw" "/t.mbox.gz"))))
      (piem-with-url-contents url
        (unless message-only
          (piem-gunzip-buffer))
        (pcase-let ((`(,added-count . ,skipped-count)
                     (piem--write-mbox-to-maildir maildir-directory)))
          (message "Added %d message%s%s for %s to %s"
                   added-count
                   (if (= added-count 1) "" "s")
                   (if (> skipped-count 0)
                       (format " (skipping %d)" skipped-count)
                     "")
                   mid
                   (abbreviate-file-name maildir-directory))))
      (run-hook-with-args 'piem-after-mail-injection-functions mid))))


;;;; Patch handling

(defun piem-am-extract-attached-patch (handle)
  "Return content for HANDLE if it looks like a patch."
  (and (listp handle)
       (let ((type (mm-handle-media-type handle))
             (filename (mm-handle-filename handle)))
         (or (member type '("text/x-diff" "text/x-patch"))
             (and filename
                  (equal type "text/plain")
                  (string-suffix-p ".patch" filename t))))
       (with-temp-buffer
         (mm-display-inline handle)
         (buffer-substring-no-properties (point-min) (point-max)))))

(defun piem-extract-mbox-info (&optional buffer)
  "Collect information from message in BUFFER.
If BUFFER is nil, the current buffer is used.  Any message after
the first will be ignored."
  (with-current-buffer (or buffer (current-buffer))
    (let ((info (cl-mapcan #'list '(:date :from :subject)
                           (piem--message-fetch-decoded-fields
                            '("date" "from" "subject")))))
      (when (re-search-forward (rx line-start "base-commit: "
                                   (group (>= 40 hex-digit))
                                   line-end)
                               nil t)
        (plist-put info :base-commit (match-string 1)))
      info)))

(defvar piem-patch-subject-re
  (rx (zero-or-more space) "["
      (zero-or-more (not (any "]" "\n")))
      "PATCH"
      (zero-or-more (not (any "]" "\n")))
      "]" (one-or-more space)))

(defun piem--shorten-subject (subject)
  (let ((words
         (mapcar #'downcase
                 (split-string
                  (thread-last subject
                    (replace-regexp-in-string
                     (rx (any "'\""))
                     "")
                    (replace-regexp-in-string
                     piem-patch-subject-re ""))
                  "\\W+" t)))
        (ignore-these (list "a" "an" "the"))
        (num-words 0)
        (num-chars 0)
        kept)
    (catch 'stop
      (dolist (word words)
        (when (not (member word ignore-these))
          (cl-incf num-words)
          (cl-incf num-chars (length word))
          (push word kept)
          (when (or (> num-words 5)
                    (> num-chars 20))
            (throw 'stop nil)))))
    (mapconcat #'identity (reverse kept) "-")))

(defun piem-name-branch-who-what-v (info)
  "Construct a branch name like \"km/b4-short-subj__v3\".

In the above example, \"k\" and \"m\" are the first letters of
the first and second \"words\" in the \"From:\" field.
\"b4-short-subj\" is a stripped down, truncated variant of
\"Subject:\".  And \"v3\" is the version of the patch series, as
indicated in the subject.

INFO is a plist with properties documented
in `piem-default-branch-function'."
  (when-let ((from (plist-get info :from))
             (sender (let ((mail-extr-ignore-single-names nil)
                           (mail-extr-ignore-realname-equals-mailbox-name nil))
                       (car (mail-extract-address-components from))))
             (subject (plist-get info :subject)))
    (let* ((subnames (split-string sender))
           (initials (mapconcat
                      (lambda (subname)
                        (and subname
                             (downcase (substring subname nil 1))))
                      (list (car subnames) (cadr subnames))
                      ""))
           (version (and (string-match
                          (rx "[" (zero-or-more (not (any "[" "\n")))
                              "PATCH "
                              (zero-or-one (group "v" (one-or-more digit))))
                          subject)
                         (match-string 1 subject))))
      (concat initials "/"
              (piem--shorten-subject subject)
              (and version (concat "__" version))))))

(defvar piem-am-args (list "--scissors" "--3way"))

(defun piem-am-read-worktree (coderepo branch)
  "Read a worktree to create for applying patches.
This function is intended to be used as a value of
`piem-am-read-worktree-function'.  The worktree directory is
completed from the parent directory of CODEREPO.  If BRANCH is
non-nil, it is used to construct the default completion value."
  (let ((fname (directory-file-name coderepo)))
    (read-directory-name
     "Create worktree: "
     (file-name-directory fname) nil nil
     (and branch
          (concat (file-name-nondirectory fname) "-"
                  (replace-regexp-in-string "/" "-" branch))))))

;;;###autoload
(defun piem-am (mbox &optional format info coderepo toggle-worktree)
  "Feed an am-ready mbox to `git am'.

MBOX is a buffer whose contents are an am-ready mbox (obtained
via `piem-am-ready-mbox' when called interactively).  FORMAT
controls the value passed as the --patch-format option of `git
am'.  \"mbox\" and \"mboxrd\" are valid values, and \"mboxrd\" is
the default.

INFO is a plist that with information to help choose a default
branch name or starting point (see `piem-default-branch-function'
for a list of possible properties).

CODEREPO, if given, indicates the code repository to operate
within.  If not specified, the default directory is used.

When prefix argument TOGGLE-WORKTREE is non-nil, invert the
meaning of `piem-am-create-worktree'.  With the default value,
this triggers the creation of a new worktree."
  (interactive
   (pcase-let ((`(,mbox . ,format)
                (or (piem-am-ready-mbox)
                    (user-error
                     "Could not find am-ready mbox for current buffer"))))
     ;; We're responsible for cleaning up the buffer created by
     ;; `piem-am-ready-mbox'; sneak in an indication to let the
     ;; downstream code know.
     (list (cons :interactive mbox)
           format
           (piem-extract-mbox-info mbox)
           (piem-inbox-coderepo-maybe-read)
           current-prefix-arg)))
  (setq format (or format "mboxrd"))
  (let* ((default-directory (or coderepo default-directory))
         (am-directory default-directory)
         (use-worktree (xor piem-am-create-worktree toggle-worktree))
         (interactivep (eq (car-safe mbox) :interactive)))
    (when interactivep
      (setq mbox (cdr mbox)))
    (let ((new-branch
           (let ((b (read-string "New branch (empty for detached): "
                                 (funcall piem-default-branch-function info))))
             (and (not (string-empty-p b)) b)))
          (base (completing-read
                 "Base commit: "
                 (let ((cands (and piem-use-magit
                                   (fboundp 'magit-list-local-branch-names)
                                   (magit-list-local-branch-names)))
                       (base (plist-get info :base-commit)))
                   (if base (cons base cands) cands)))))
      (when use-worktree
        (setq am-directory
              (expand-file-name
               (funcall piem-am-read-worktree-function
                        default-directory new-branch)))
        (when (file-exists-p am-directory)
          (user-error "Worktree directory already exists")))
      (apply #'piem-process-call nil piem-git-executable
             (append (if use-worktree
                         (list "worktree" "add")
                       (list "checkout"))
                     (if new-branch (list "-b" new-branch) (list "--detach"))
                     (and use-worktree (list am-directory))
                     (and (not (string-blank-p base))
                          (list base)))))
    (let ((args (cons (concat "--patch-format=" format)
                      piem-am-args)))
      (if (bufferp mbox)
          (unwind-protect
              (apply #'piem-process-call-with-buffer-input
                     am-directory mbox piem-git-executable "am" args)
            (when interactivep
              (kill-buffer mbox)))
        (apply #'piem-process-call am-directory piem-git-executable "am"
               (append args (list mbox)))))
    (if (and piem-use-magit
             (fboundp 'magit-status-setup-buffer))
        (magit-status-setup-buffer am-directory)
      (dired am-directory))))


;;;; Dispatch

;;;###autoload (autoload 'piem-dispatch "piem" nil t)
(transient-define-prefix piem-dispatch ()
  "Invoke a piem command."
  [[("a" "apply patch" piem-am)
    ("b" "call b4-am" piem-b4-am)]
   [("i" "inject thread into maildir" piem-inject-thread-into-maildir)
    ("l" "copy public-inbox link" piem-copy-mid-url)]])



(defun piem-please ()
  "How I wish I could intersect my emails, feeds, and repos")

;;; piem.el ends here
(provide 'piem)