bug#52507: [PATCH v3] Option for vc-delete-file to keep file on disk

[Ashwin Kafle <ashwin@ashwink.com.np>]

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Dmitry Gutov <dgutov@yandex.ru> writes:

[...]
>> But then the user will get error about wrong number of arguments if
>> the
>> backend doesn't support it.
>
> That's better than having the file deleted, I think.
>
> And our implementation can catch this particular error and show a more
> humane message, too.

With the attached patch, the file will not be deleted when prefix is given.


[...]
>> I think it would be better to check if the file exists after calling
>> vc
>> backends.  If it doesn't and keep-files is non-nil, we can restore from the
>> backup(which is always happening).
>
> Couldn't backups be disabled?

The attached patch changes make-backup-files temporarily.


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From 846a92e9623a05d49d0026a62697a39d0e7690a7 Mon Sep 17 00:00:00 2001
From: Ashwin Kafle <ashwin@ashwink.com.np>
Date: Wed, 15 Dec 2021 23:49:47 +0545
Subject: [PATCH] Option for vc-delete-file to keep file on disk

Add a prefix argument on vc-delete-file to keep affected
file on disk and keep the current buffer intact.  This option
relies on the backends to not delete files themselves.

* doc/emacs/vc1-xtra.texi: Document the change.
* lisp/vc/vc-git.el (vc-git-delete-file): Make git leave files on disk.
* lisp/vc/vc.el (vc-delete-file): Change vc-delete-file to accept
optional prefix argument. Also have it manage backup files in
case the backend delets files when we don't want to.
---
 doc/emacs/vc1-xtra.texi |  3 ++-
 etc/NEWS                |  4 ++++
 lisp/vc/vc-git.el       |  4 ++--
 lisp/vc/vc.el           | 32 +++++++++++++++++++++-----------
 4 files changed, 29 insertions(+), 14 deletions(-)

diff --git a/doc/emacs/vc1-xtra.texi b/doc/emacs/vc1-xtra.texi
index 4cd00cba6c..99e5eef7c1 100644
--- a/doc/emacs/vc1-xtra.texi
+++ b/doc/emacs/vc1-xtra.texi
@@ -122,7 +122,8 @@ VC Delete/Rename
   If you wish to delete a version-controlled file, use the command
 @kbd{M-x vc-delete-file}.  This prompts for the file name, and deletes
 it via the version control system.  The file is removed from the
-working tree, and in the VC Directory buffer
+working tree, and in the VC Directory buffer.  If you give a prefix argument,
+the file is not deleted from disk.
 @iftex
 (@pxref{VC Directory Mode,,, emacs, the Emacs Manual}),
 @end iftex
diff --git a/etc/NEWS b/etc/NEWS
index 8d83b2a7e3..af358aaedb 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -372,6 +372,10 @@ info node.  This command only works for the Emacs and Emacs Lisp manuals.
 
 ** vc
 
+*** 'C-x v x' accepts a prefix argument to keep file on disk.
+Previously 'C-x v x' always deleted the selected file.  Now if you give it
+prefix argument, it will keep the buffer and file on disk intact.
+Currently this is only implemented for vc-git.
 ---
 *** 'C-x v v' on an unregistered file will now use the most specific backend.
 Previously, if you had an SVN-covered "~/" directory, and a Git-covered
diff --git a/lisp/vc/vc-git.el b/lisp/vc/vc-git.el
index 5c6a39aec9..69ef216529 100644
--- a/lisp/vc/vc-git.el
+++ b/lisp/vc/vc-git.el
@@ -1569,8 +1569,8 @@ vc-git-next-revision
     (or (vc-git-symbolic-commit next-rev) next-rev)))
 
 (defun vc-git-delete-file (file)
-  (vc-git-command nil 0 (vc-git--literal-pathspec file) "rm" "-f" "--"))
-
+  (vc-git-command nil 0 (vc-git--literal-pathspec file) "rm" "-f" "--cached" "--"))
+)
 (defun vc-git-rename-file (old new)
   (vc-git-command nil 0 (list old new) "mv" "-f" "--"))
 
diff --git a/lisp/vc/vc.el b/lisp/vc/vc.el
index 64f752f248..8d393282cc 100644
--- a/lisp/vc/vc.el
+++ b/lisp/vc/vc.el
@@ -2970,14 +2970,17 @@ vc-transfer-file
       (vc-checkin file new-backend comment (stringp comment)))))
 
 ;;;###autoload
-(defun vc-delete-file (file)
+(defun vc-delete-file (file &optional keep-file)
   "Delete file and mark it as such in the version control system.
 If called interactively, read FILE, defaulting to the current
-buffer's file name if it's under version control."
+buffer's file name if it's under version control.
+If a prefix argument is given (optional argument KEEP-FILE) then
+don't delete the file from the disk."
   (interactive (list (read-file-name "VC delete file: " nil
                                      (when (vc-backend buffer-file-name)
                                        buffer-file-name)
-                                     t)))
+                                     t)
+                     current-prefix-arg))
   (setq file (expand-file-name file))
   (let ((buf (get-file-buffer file))
         (backend (vc-backend file)))
@@ -2996,22 +2999,29 @@ vc-delete-file
     (unless (y-or-n-p (format "Really want to delete %s? "
 			      (file-name-nondirectory file)))
       (error "Abort!"))
-    (unless (or (file-directory-p file) (null make-backup-files)
-                (not (file-exists-p file)))
+    (when (or (not (file-directory-p file))
+              (file-exists-p file))
       (with-current-buffer (or buf (find-file-noselect file))
-	(let ((backup-inhibited nil))
+	(let ((backup-inhibited nil)
+              (make-backup-files t)
+              ;; If you don't set this, then for some reason, the file is never brought back.
+              (backup-by-copying t))
 	  (backup-buffer))))
     ;; Bind `default-directory' so that the command that the backend
     ;; runs to remove the file is invoked in the correct context.
     (let ((default-directory (file-name-directory file)))
       (vc-call-backend backend 'delete-file file))
-    ;; If the backend hasn't deleted the file itself, let's do it for him.
-    (when (file-exists-p file) (delete-file file))
+    ;; If the file dosen't exist when we want to or vice-versa, fix that.
+    (let ((back-file (car (file-backup-file-names file))))
+      (if (file-exists-p file)
+          (if (not keep-file) (delete-file file))
+        (when (and keep-file back-file)
+          (copy-file back-file file t t t t)))
+      (unless make-backup-files (delete-file back-file)))
     ;; Forget what VC knew about the file.
     (vc-file-clearprops file)
-    ;; Make sure the buffer is deleted and the *vc-dir* buffers are
-    ;; updated after this.
-    (vc-resynch-buffer file nil t)))
+    ;; Make sure the *vc-dir* buffers are updated after this.
+    (vc-resynch-buffer file keep-file t)))
 
 ;;;###autoload
 (defun vc-rename-file (old new)
-- 
2.34.1