Merge branch 'jk/two-way-merge-corner-case-fix' into maint

"git am --abort" sometimes complained about not being able to write
a tree with an 0{40} object in it.

* jk/two-way-merge-corner-case-fix:
  t1005: add test for "read-tree --reset -u A B"
  t1005: reindent
  unpack-trees: fix "read-tree -u --reset A B" with conflicted index

t/t1005-read-tree-reset.sh

@@ -43,6 +43,21 @@ test_expect_success 'reset should remove remnants from a failed merge' '
 	! test -f old
 '
 
+test_expect_success 'two-way reset should remove remnants too' '
+	read_tree_u_must_succeed --reset -u HEAD &&
+	git ls-files -s >expect &&
+	sha1=$(git rev-parse :new) &&
+	(
+		echo "100644 $sha1 1	old"
+		echo "100644 $sha1 3	old"
+	) | git update-index --index-info &&
+	>old &&
+	git ls-files -s &&
+	read_tree_u_must_succeed --reset -u HEAD HEAD &&
+	git ls-files -s >actual &&
+	! test -f old
+'
+
 test_expect_success 'Porcelain reset should remove remnants too' '
 	read_tree_u_must_succeed --reset -u HEAD &&
 	git ls-files -s >expect &&

unpack-trees.c

@@ -1763,7 +1763,16 @@ int twoway_merge(const struct cache_entry * const *src,
 		newtree = NULL;
 
 	if (current) {
-		if ((!oldtree && !newtree) || /* 4 and 5 */
+		if (current->ce_flags & CE_CONFLICTED) {
+			if (same(oldtree, newtree) || o->reset) {
+				if (!newtree)
+					return deleted_entry(current, current, o);
+				else
+					return merged_entry(newtree, current, o);
+			}
+			return o->gently ? -1 : reject_merge(current, o);
+		}
+		else if ((!oldtree && !newtree) || /* 4 and 5 */
 			 (!oldtree && newtree &&
 			  same(current, newtree)) || /* 6 and 7 */
 			 (oldtree && newtree &&