(declare-function rx-to-string "rx" (form &optional no-group))

(declare-function vc-exec-after "vc-dispatcher" (code))
(declare-function vc-set-async-update "vc-dispatcher" (process-buffer))

(defun vc-pijul-find-revision (file rev buffer)
  "Fetch REVISION for FILE and put into BUFFER.
I don't know how to do this without creating a new channel.  But
it is weird to create a new channel just to do this thing."
  (user-error "unimplemented!"))
(defun vc-pijul-checkout (file &optional rev)
  "Check out REVISION for FILE.
I don't know how to do this without creating a new channel.  But
it is weird to create a new channel just to do this thing."
  (user-error "unimplemented!"))
(defun vc-pijul-revert (file &optional contents-done)
  "Revert FILE to the working revision.
If CONTENTS-DONE is non-nil, we only need to remove the FILE, if
it is already added but not commited yet."
  ;; TODO
  )
(defvar log-view-message-re)
(defvar log-view-file-re)
(defvar log-view-font-lock-keywords)
(defvar log-view-per-file-logs)
(defvar log-view-expanded-log-entry-function)
(defvar pijul-log-view-format
  (list
   (rx-to-string
    '(seq bol "Change"
      (one-or-more space)
      (group-n 1
       (one-or-more
        (any
         (?a . ?z)
         (?A . ?Z)
         digit)))
      (any ?\n ?\r))
    t)
   (list 1 ''log-view-message))
  "The format for `vc-pijul-log-view-mode'.
The first element is the regular expression to match the first
line of a log.  Its first capture group is required to match
exactly the revision number.
The following elements are font lock keywords.")

(define-derived-mode vc-pijul-log-view-mode log-view-mode
  "Pijul-Log-View"
  "Major mode for viewing logs of pijul."
  ;; We need some faces from add-log.
  (require 'add-log)
  ;; There are no file markers, so this should match nothing.
  (setq-local log-view-file-re regexp-unmatchable)
  (setq-local log-view-per-file-logs nil)
  (setq-local log-view-message-re (car pijul-log-view-format))
  (setq-local log-view-font-lock-keywords
              (cons
               pijul-log-view-format
               (list
                (list
                 ;; only email
                 (rx-to-string
                  '(seq bol "Author:"
                    (one-or-more space)
                    (group-n 1
                     (one-or-more
                      (any
                       (?a . ?z) (?A . ?Z)
                       (?0 . ?9) ?_ ?. ?+ ?-))
                     ?@
                     (one-or-more
                      (any
                       (?a . ?z) (?A . ?Z)
                       (?0 . ?9) ?_ ?. ?-))))
                  t)
                 (list 1 ''change-log-email))
                (list
                 ;; only name
                 (rx-to-string
                  '(seq bol "Author:"
                    (one-or-more space)
                    (group-n 1 (one-or-more (not (or ?< ?\n ?\r))))
                    (zero-or-more space))
                  t)
                 (list 1 ''change-log-name))
                (list
                 ;; name and email
                 (rx-to-string
                  '(seq bol "Author:"
                    (one-or-more space)
                    (group-n 1 (+? (not ?<)))
                    (zero-or-more space)
                    ?<
                    (group-n 2
                     (one-or-more
                      (any
                       (?a . ?z) (?A . ?Z)
                       (?0 . ?9) ?_ ?+ ?- ?.))
                     ?@
                     (one-or-more
                      (any
                       (?a . ?z) (?A . ?Z)
                       (?0 . ?9) ?_ ?- ?.)))
                    ?>)
                  t)
                 (list 1 ''change-log-name)
                 (list 2 ''change-log-email))
                (list
                 ;; Date
                 (rx-to-string
                  '(seq bol "Date:"
                    (one-or-more space)
                    (group-n 1 (one-or-more not-newline)))
                  t)
                 (list 1 ''change-log-date))))))

(declare-function log-edit-mode "log-edit" ())
(declare-function log-edit-toggle-header "log-edit" (header value))
(declare-function log-edit-extract-headers "log-edit" (headers string))
(declare-function log-edit--toggle-amend "log-edit" (last-msg-fn))