Revert "merge-ort: ignore the directory rename split conflict for now"

This reverts commit 5ced7c3da0, which was
put in place as a temporary measure to avoid optimizations unstably
erroring out on no destination having a majority of the necessary
renames for directories that had no new files and thus no need for
directory rename detection anyway.  Now that optimizations are in place
to prevent us from trying to compute directory rename count computations
for directories that do not need it, we can undo this temporary measure.

Signed-off-by: Elijah Newren <newren@gmail.com>
Reviewed-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

merge-ort.c

@@ -1636,18 +1636,7 @@ static void get_provisional_directory_renames(struct merge_options *opt,
 				 "no destination getting a majority of the "
 				 "files."),
 			       source_dir);
-			/*
-			 * We should mark this as unclean IF something attempts
-			 * to use this rename.  We do not yet have the logic
-			 * in place to detect if this directory rename is being
-			 * used, and optimizations that reduce the number of
-			 * renames cause this to falsely trigger.  For now,
-			 * just disable it, causing t6423 testcase 2a to break.
-			 * We'll later fix the detection, and when we do we
-			 * will re-enable setting *clean to 0 (and thereby fix
-			 * t6423 testcase 2a).
-			 */
-			/*   *clean = 0;   */
+			*clean = 0;
 		} else {
 			strmap_put(&renames->dir_renames[side],
 				   source_dir, (void*)best);