Fix fontification in short unintegrated changes logs (bug#81215)

Do not merge to master.

* lisp/vc/vc.el (vc--shortlog): New variable.
(vc-print-log-internal):
* lisp/vc/vc-git.el (vc-git-log-view-mode):
* lisp/vc/vc-hg.el (vc-hg-log-view-mode): Use it.

lisp/vc/vc-git.el

@@ -1975,17 +1975,22 @@ log entries."
   (setq-local log-view-file-re regexp-unmatchable)
   (setq-local log-view-per-file-logs nil)
   (setq-local log-view-message-re
-              (if (not (memq vc-log-view-type '(long log-search with-diff)))
+              (if (if (eq vc-log-view-type 'log-unintegrated)
+                      vc--shortlog
+                    (not (memq vc-log-view-type '(long log-search with-diff))))
                   (cadr vc-git-root-log-format)
                 "^commit +\\([0-9a-z]+\\)"))
   ;; Allow expanding short log entries.
-  (when (memq vc-log-view-type
-              '(short log-outgoing log-incoming log-unintegrated mergebase))
+  (when (if (eq vc-log-view-type 'log-unintegrated)
+            vc--shortlog
+          (memq vc-log-view-type '(short log-outgoing log-incoming mergebase)))
     (setq truncate-lines t)
     (setq-local log-view-expanded-log-entry-function
                 'vc-git-expanded-log-entry))
   (setq-local log-view-font-lock-keywords
-       (if (not (memq vc-log-view-type '(long log-search with-diff)))
+       (if (if (eq vc-log-view-type 'log-unintegrated)
+               vc--shortlog
+             (not (memq vc-log-view-type '(long log-search with-diff))))
 	   (list (cons (nth 1 vc-git-root-log-format)
 		       (nth 2 vc-git-root-log-format)))
 	 (append

lisp/vc/vc-hg.el

@@ -471,8 +471,9 @@ the log starting from that revision."
 
 (define-derived-mode vc-hg-log-view-mode log-view-mode "Hg-Log-View"
   (require 'add-log) ;; we need the add-log faces
-  (let ((shortp (memq vc-log-view-type
-                      '(short log-incoming log-outgoing log-unintegrated))))
+  (let ((shortp (if (eq vc-log-view-type 'log-unintegrated)
+                    vc--shortlog
+                  (memq vc-log-view-type '(short log-incoming log-outgoing)))))
    (setq-local log-view-file-re regexp-unmatchable)
    (setq-local log-view-per-file-logs nil)
    (setq-local log-view-message-re

lisp/vc/vc.el

@@ -4309,6 +4309,13 @@ button for.  Same for CURRENT-REVISION.  LIMIT means the usual."
       "Show the log for the file name(s) %s the rename"
       before-after))))
 
+(defvar-local vc--shortlog nil
+  "Whether this is a shortlog.
+This is a hack to fix bug#81215 which came up after the Emacs 31 freeze.
+For Emacs 32 that bug is fixed by replacing `vc-log-view-type' with
+`vc-log-view-types'.")
+(put 'vc--shortlog 'permanent-local t)
+
 (defun vc-print-log-internal (backend files working-revision
                                       &optional is-start-revision limit type)
   "For specified BACKEND and FILES, show the VC log.
@@ -4328,6 +4335,7 @@ LIMIT can also be a string, which means the revision before which to stop."
       (vc-log-internal-common
        backend buffer-name files type
        (lambda (bk buf _type-arg files-arg)
+         (with-current-buffer buf (setq-local vc--shortlog shortlog))
          (vc-call-backend bk 'print-log files-arg buf shortlog
                           (when is-start-revision working-revision) limit)
          (when log-view-vc-prev-fileset