[PATCH/RFC 2/2] merge-recursive: Handle rename/rename/delete/delete conflicts.

[Nicolas Cavallari <nicolas.cavallari@green-communications.fr>]

On a rename 2to1 conflict, where both a and b are renamed to c,
the other branch may have deleted a or b.  This currently luckily
works for files but fails for symlinks.

Fix conflict_rename_rename_2to1 to not merge_file_special_markers()
with diff_filespecs where mode == 0.  The alternative would be to make
merge_file_1() handle it.

Mark the corresponding testcase in t6042 as fixed.

Signed-off-by: Nicolas Cavallari <nicolas.cavallari@green-communications.fr>
---
 merge-recursive.c                    | 28 ++++++++++++++++++++++------
 t/t6042-merge-rename-corner-cases.sh |  2 +-
 2 files changed, 23 insertions(+), 7 deletions(-)

diff --git a/merge-recursive.c b/merge-recursive.c
index b7ff1ada3..0e5a3e3ed 100644
--- a/merge-recursive.c
+++ b/merge-recursive.c
@@ -1305,13 +1305,29 @@ static int conflict_rename_rename_2to1(struct merge_options *o,
 	remove_file(o, 1, a->path, o->call_depth || would_lose_untracked(a->path));
 	remove_file(o, 1, b->path, o->call_depth || would_lose_untracked(b->path));
 
-	if (merge_file_special_markers(o, a, c1, &ci->ren1_other,
-				       o->branch1, c1->path,
-				       o->branch2, ci->ren1_other.path, &mfi_c1) ||
-	    merge_file_special_markers(o, b, &ci->ren2_other, c2,
-				       o->branch1, ci->ren2_other.path,
-				       o->branch2, c2->path, &mfi_c2))
+	// The other branch may have deleted a, as indicated by mode == 0.
+	if (ci->ren1_other.mode == 0) {
+		mfi_c1.clean = 0;
+		mfi_c1.merge = 0;
+		mfi_c1.mode = c1->mode;
+		oidcpy(&mfi_c1.oid, &c1->oid);
+	} else if (merge_file_special_markers(o, a, c1, &ci->ren1_other,
+					      o->branch1, c1->path,
+					      o->branch2, ci->ren1_other.path,
+					      &mfi_c1)) {
 		return -1;
+	}
+
+	if (ci->ren2_other.mode == 0) {
+		mfi_c2.clean = 0;
+		mfi_c2.merge = 0;
+		mfi_c2.mode = c2->mode;
+		oidcpy(&mfi_c2.oid, &c2->oid);
+	} else if (merge_file_special_markers(o, b, &ci->ren2_other, c2,
+					      o->branch1, ci->ren2_other.path,
+					      o->branch2, c2->path, &mfi_c2)) {
+		return -1;
+	}
 
 	if (o->call_depth) {
 		/*
diff --git a/t/t6042-merge-rename-corner-cases.sh b/t/t6042-merge-rename-corner-cases.sh
index ea4e14cbd..34b16d5d7 100755
--- a/t/t6042-merge-rename-corner-cases.sh
+++ b/t/t6042-merge-rename-corner-cases.sh
@@ -605,7 +605,7 @@ test_expect_success 'setup rename/rename/delete/delete conflict' '
 	git commit -m C
 '
 
-test_expect_failure 'rename/rename/delete/delete leaves at least one file' '
+test_expect_success 'rename/rename/delete/delete leaves at least one file' '
 	git checkout B^0 &&
 	test_must_fail git merge -s recursive C^0 &&
 
-- 
2.11.0