mv: check overwrite for in-to-out move

Add checking logic for overwriting when moving from in-cone to
out-of-cone. It is the index version of the original overwrite logic.

Helped-by: Derrick Stolee <derrickstolee@github.com>
Signed-off-by: Shaoxuan Yuan <shaoxuan.yuan02@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/mv.c

@@ -376,6 +376,18 @@ dir_check:
 			goto act_on_entry;
 		}
 
+		if (ignore_sparse &&
+		    (dst_mode & (SKIP_WORKTREE_DIR | SPARSE)) &&
+		    index_entry_exists(&the_index, dst, strlen(dst))) {
+			bad = _("destination exists in the index");
+			if (force) {
+				if (verbose)
+					warning(_("overwriting '%s'"), dst);
+				bad = NULL;
+			} else {
+				goto act_on_entry;
+			}
+		}
 		/*
 		 * We check if the paths are in the sparse-checkout
 		 * definition as a very final check, since that

t/t7002-mv-sparse-checkout.sh

@@ -323,7 +323,7 @@ test_expect_success 'move clean path from in-cone to out-of-cone' '
 	grep "S folder1/d" actual
 '
 
-test_expect_failure 'move clean path from in-cone to out-of-cone overwrite' '
+test_expect_success 'move clean path from in-cone to out-of-cone overwrite' '
 	test_when_finished "cleanup_sparse_checkout" &&
 	setup_sparse_checkout &&
 	echo "sub/file1 overwrite" >sub/file1 &&
@@ -359,7 +359,7 @@ test_expect_failure 'move clean path from in-cone to out-of-cone overwrite' '
 # This test is testing the same behavior as the
 # "move clean path from in-cone to out-of-cone overwrite" above.
 # The only difference is the <destination> changes from "folder1" to "folder1/file1"
-test_expect_failure 'move clean path from in-cone to out-of-cone file overwrite' '
+test_expect_success 'move clean path from in-cone to out-of-cone file overwrite' '
 	test_when_finished "cleanup_sparse_checkout" &&
 	setup_sparse_checkout &&
 	echo "sub/file1 overwrite" >sub/file1 &&
@@ -392,7 +392,7 @@ test_expect_failure 'move clean path from in-cone to out-of-cone file overwrite'
 	test_cmp expect actual
 '
 
-test_expect_failure 'move directory with one of the files overwrite' '
+test_expect_success 'move directory with one of the files overwrite' '
 	test_when_finished "cleanup_sparse_checkout" &&
 	mkdir -p folder1/dir &&
 	touch folder1/dir/file1 &&