bug#60011: 30.0.50; git commit from *vc-diff* does not work over tramp

[Juri Linkov <juri@linkov.net>]

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Hi Michael,

Could you please confirm that I correctly implemented support for
Tramp in the following patch.

>> I run Emacs locally (macosx laptop) and edit remote (Amazon Linux "cloud
>> desktop") files using tramp (scp).
>> I can commit files using vc/git just fine.
>> However, when I edit *vc-diff* and hit C-v v v (vc-next-action), and
>> then edit the commit message abd hit C-c C-c, I get this error:
>> Debugger entered--Lisp error: (error "Failed (status 128): git --no-pager apply --cached...")
>
> The problem is in these lines that create a temporary file
> on a local directory only:


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diff --git a/lisp/vc/vc-git.el b/lisp/vc/vc-git.el
index 83138a6d107..65604e84d0e 100644
--- a/lisp/vc/vc-git.el
+++ b/lisp/vc/vc-git.el
@@ -103,6 +103,7 @@
 (require 'vc-dispatcher)
 (eval-when-compile
   (require 'subr-x) ; for string-trim-right
+  (require 'tramp)
   (require 'vc)
   (require 'vc-dir))
 
@@ -1048,7 +1049,13 @@ vc-git-checkin
                         (string-replace file-diff "" vc-git-patch-string))
                 (user-error "Index not empty"))
               (setq pos (point))))))
-      (let ((patch-file (make-temp-file "git-patch")))
+      (let ((patch-file
+             (if (file-remote-p default-directory)
+                 (with-parsed-tramp-file-name
+                     (expand-file-name default-directory) nil
+                   (tramp-make-tramp-file-name
+                    v (with-no-warnings (tramp-make-tramp-temp-file v))))
+               (make-temp-file "git-patch"))))
         (with-temp-file patch-file
           (insert vc-git-patch-string))
         (unwind-protect