bug#46538: Patch: wrap around smerge-vc-next-conflict if current file still has conflicts

[Konstantin Kharlamov <hi-angel@yandex.ru>]

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Currently, if the buffer has conflict markers above the (point) and it's the last conflicted file, we bail out. A user pointed out¹ that it is a good idea to try to find conflicts in the current file as well. Indeed, it seems like more correct behaviour: going to the next conflict is whole purpose of the function, and current file might still have them.

Attached patch implements additional check for conflicts just for the case when the buffer is the last conflicted file and all conflicts are above current point.

1: https://emacs.stackexchange.com/questions/63413/finding-git-conflict-in-the-same-buffer-if-cursor-is-at-end-of-the-buffer

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From f8d8f1cbdb94f75765165acacd089f1e3cc4a763 Mon Sep 17 00:00:00 2001
From: Konstantin Kharlamov <Hi-Angel@yandex.ru>
Date: Mon, 15 Feb 2021 21:37:33 +0300
Subject: [PATCH] vc: make smerge-vc-next-conflict wrap around

lisp/vc/smerge-mode.el:
(smerge-next-safe): a wrapper around smerge-next that doesn't throw
an error.
(smerge-vc-next-conflict): make it wrap around a file if it's the last
conflicted file, and it still has conflicts
---
 lisp/vc/smerge-mode.el | 20 ++++++++++++++------
 1 file changed, 14 insertions(+), 6 deletions(-)

diff --git a/lisp/vc/smerge-mode.el b/lisp/vc/smerge-mode.el
index 3b09dfe5d2..0558240120 100644
--- a/lisp/vc/smerge-mode.el
+++ b/lisp/vc/smerge-mode.el
@@ -1446,6 +1446,14 @@ smerge-change-buffer-confirm
   "If non-nil, request confirmation before moving to another buffer."
   :type 'boolean)
 
+(defun smerge-next-safe ()
+    "Tries to move to next conflict, returns t on success, nil
+otherwise"
+  (condition-case err
+      (not (smerge-next))
+    ('error
+     nil)))
+
 (defun smerge-vc-next-conflict ()
   "Go to next conflict, possibly in another file.
 First tries to go to the next conflict in the current buffer, and if not
@@ -1469,12 +1477,12 @@ smerge-vc-next-conflict
          (if (and (buffer-modified-p) buffer-file-name)
              (save-buffer))
          (vc-find-conflicted-file)
-         (if (eq buffer (current-buffer))
-             ;; Do nothing: presumably `vc-find-conflicted-file' already
-             ;; emitted a message explaining there aren't any more conflicts.
-             nil
-           (goto-char (point-min))
-           (smerge-next)))))))
+         (when (eq buffer (current-buffer))
+           ;; try to find a conflict marker in current file above the point
+           (let ((prev-pos (point)))
+             (goto-char (point-min))
+             (when (not (smerge-next-safe))
+               (goto-char prev-pos)))))))))
 
 (provide 'smerge-mode)
 
-- 
2.30.1