merge-recursive: Avoid excessive output for and reprocessing of renames

In 5a2580d (merge_recursive: Fix renames across paths below D/F conflicts
2010-07-09) and ae74548 (merge-recursive: Fix multiple file rename across
D/F conflict 2010-08-17), renames across D/F conflicts were fixed by
making process_renames() consider as unprocessed renames whose dst_entry
"still" had higher stage entries.  The assumption was that those higher
stage entries would have been cleared out of dst_entry by that point in
cases where the conflict could be resolved (normal renames with no D/F
conflicts).  That is not the case -- higher stage entries will remain in
all cases.

Fix this by checking for higher stage entries corresponding to D/F
conflicts, namely that stages 2 and 3 have exactly one nonzero mode between
them.  The nonzero mode stage corresponds to a file at the path, while the
stage with a zero mode will correspond to a directory at that path (since
rename/delete conflicts will have already been handled before this codepath
is reached.)

Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: newren

merge-recursive.c

@@ -1020,7 +1020,6 @@ static int process_renames(struct merge_options *o,
 				if (mfi.clean &&
 				    sha_eq(mfi.sha, ren1->pair->two->sha1) &&
 				    mfi.mode == ren1->pair->two->mode) {
-					int i;
 					/*
 					 * This message is part of
 					 * t6022 test. If you change
@@ -1032,12 +1031,9 @@ static int process_renames(struct merge_options *o,
 					 * in the index (e.g. due to a D/F
 					 * conflict) that need to be resolved.
 					 */
-					for (i = 1; i <= 3; i++) {
-						if (!ren1->dst_entry->stages[i].mode)
-							continue;
+					if (!ren1->dst_entry->stages[2].mode !=
+					    !ren1->dst_entry->stages[3].mode)
 						ren1->dst_entry->processed = 0;
-						break;
-					}
 				} else {
 					if (mfi.merge || !mfi.clean)
 						output(o, 1, "Renaming %s => %s", ren1_src, ren1_dst);