Subject: Re: bug#68443: 30.0.50; Cannot commit from *vc-diff* if there is a deleted file.

From: Dmitry Gutov <[email-masked]>
Date: Wed, 17 Jan 2024 06:25:34 +0200

Hi! Thanks for the report.

On 13/01/2024 15:56, Aleksandr Vityazev via Bug reports for GNU Emacs, 
the Swiss army knife of text editors wrote:
> Hi,
> 
> Steps to reproduce with emacs -q:
> 
> 1. Enter git repository;
> 2. vc-delete-file some file;
> 3. vc-root-diff;
> 4. From *vc-diff* buffer vc-next-action;
> 5. In *vc-log* write summary and invoke vc-next-action;
> 6. get error (wrong-type-argument stringp nil)
> 
> Full backtrace:
> 
> Debugger entered--Lisp error: (wrong-type-argument stringp nil)
>    file-directory-p(nil)
>    #f(compiled-function (files comment) #<bytecode 0x1e31e0a127714b22>)((#(".gitignore" 0 10 (fontified t face (diff-file-header diff-header))) #("buffer.c" 0 8 (fontified t face (diff-file-header diff-header))) nil) #("Summary: Delete file.\n" 0 8 (jit-lock-defer-multiline t face log-edit-header fontified t field header) 8 9 (jit-lock-defer-multiline t fontified t field header) 9 21 (jit-lock-defer-multiline t face log-edit-summary fontified t field header) 21 22 (fontified t)))
>    vc-finish-logentry()
>    funcall-interactively(vc-finish-logentry)
>    log-edit-done()
>    funcall-interactively(log-edit-done)
>    command-execute(log-edit-done)

Try the patch below, seems to work here:

diff --git a/lisp/vc/diff-mode.el b/lisp/vc/diff-mode.el
index 03efe0fdb31..83d580d98dd 100644
--- a/lisp/vc/diff-mode.el
+++ b/lisp/vc/diff-mode.el
@@ -3014,7 +3014,7 @@ diff-vc-deduce-fileset
        (goto-char (point-min))
        (while (progn (diff-file-next) (not (eobp)))
          (push (diff-find-file-name nil t) files)))
-    (list backend (nreverse files) nil nil 'patch)))
+    (list backend (delete nil (nreverse files)) nil nil 'patch)))

  (defun diff--filter-substring (str)
    (when diff-font-lock-prettify

(Eli, would this be suitable for emacs-29?)