merge-ort-wrappers: make printed message match the one from recursive

When the index does not match HEAD, the merge strategies are responsible
to detect that condition and abort.  The merge-ort-wrappers had code to
implement this and meant to copy the error message from merge-recursive
but deviated in two ways, both due to the message in merge-recursive
being processed by another function that made additional changes:
  * It added an implicit "error: " prefix
  * It added an implicit trailing newline
We can get these things by making use of the error() function.

Signed-off-by: Elijah Newren <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: newren

merge-ort-wrappers.c

@@ -10,8 +10,8 @@ static int unclean(struct merge_options *opt, struct tree *head)
 	struct strbuf sb = STRBUF_INIT;
 
 	if (head && repo_index_has_changes(opt->repo, head, &sb)) {
-		fprintf(stderr, _("Your local changes to the following files would be overwritten by merge:\n  %s"),
-		    sb.buf);
+		error(_("Your local changes to the following files would be overwritten by merge:\n  %s"),
+		      sb.buf);
 		strbuf_release(&sb);
 		return -1;
 	}