merge-recursive: avoid clobbering untracked files with directory renames

Reviewed-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

merge-recursive.c

@@ -1141,6 +1141,26 @@ static int conflict_rename_dir(struct merge_options *o,
 {
 	const struct diff_filespec *dest = pair->two;
 
+	if (!o->call_depth && would_lose_untracked(dest->path)) {
+		char *alt_path = unique_path(o, dest->path, rename_branch);
+
+		output(o, 1, _("Error: Refusing to lose untracked file at %s; "
+			       "writing to %s instead."),
+		       dest->path, alt_path);
+		/*
+		 * Write the file in worktree at alt_path, but not in the
+		 * index.  Instead, write to dest->path for the index but
+		 * only at the higher appropriate stage.
+		 */
+		if (update_file(o, 0, &dest->oid, dest->mode, alt_path))
+			return -1;
+		free(alt_path);
+		return update_stages(o, dest->path, NULL,
+				     rename_branch == o->branch1 ? dest : NULL,
+				     rename_branch == o->branch1 ? NULL : dest);
+	}
+
+	/* Update dest->path both in index and in worktree */
 	if (update_file(o, 1, &dest->oid, dest->mode, dest->path))
 		return -1;
 	return 0;
@@ -1159,7 +1179,8 @@ static int handle_change_delete(struct merge_options *o,
 	const char *update_path = path;
 	int ret = 0;
 
-	if (dir_in_way(path, !o->call_depth, 0)) {
+	if (dir_in_way(path, !o->call_depth, 0) ||
+	    (!o->call_depth && would_lose_untracked(path))) {
 		update_path = alt_path = unique_path(o, path, change_branch);
 	}
 
@@ -1285,6 +1306,12 @@ static int handle_file(struct merge_options *o,
 			dst_name = unique_path(o, rename->path, cur_branch);
 			output(o, 1, _("%s is a directory in %s adding as %s instead"),
 			       rename->path, other_branch, dst_name);
+		} else if (!o->call_depth &&
+			   would_lose_untracked(rename->path)) {
+			dst_name = unique_path(o, rename->path, cur_branch);
+			output(o, 1, _("Refusing to lose untracked file at %s; "
+				       "adding as %s instead"),
+			       rename->path, dst_name);
 		}
 	}
 	if ((ret = update_file(o, 0, &rename->oid, rename->mode, dst_name)))
@@ -1410,7 +1437,18 @@ static int conflict_rename_rename_2to1(struct merge_options *o,
 		char *new_path2 = unique_path(o, path, ci->branch2);
 		output(o, 1, _("Renaming %s to %s and %s to %s instead"),
 		       a->path, new_path1, b->path, new_path2);
-		remove_file(o, 0, path, 0);
+		if (would_lose_untracked(path))
+			/*
+			 * Only way we get here is if both renames were from
+			 * a directory rename AND user had an untracked file
+			 * at the location where both files end up after the
+			 * two directory renames.  See testcase 10d of t6043.
+			 */
+			output(o, 1, _("Refusing to lose untracked file at "
+				       "%s, even though it's in the way."),
+			       path);
+		else
+			remove_file(o, 0, path, 0);
 		ret = update_file(o, 0, &mfi_c1.oid, mfi_c1.mode, new_path1);
 		if (!ret)
 			ret = update_file(o, 0, &mfi_c2.oid, mfi_c2.mode,

t/t6043-merge-rename-directories.sh

@@ -2992,7 +2992,7 @@ test_expect_success '10b-setup: Overwrite untracked with dir rename + delete' '
 	)
 '
 
-test_expect_failure '10b-check: Overwrite untracked with dir rename + delete' '
+test_expect_success '10b-check: Overwrite untracked with dir rename + delete' '
 	(
 		cd 10b &&
 
@@ -3070,7 +3070,7 @@ test_expect_success '10c-setup: Overwrite untracked with dir rename/rename(1to2)
 	)
 '
 
-test_expect_failure '10c-check: Overwrite untracked with dir rename/rename(1to2)' '
+test_expect_success '10c-check: Overwrite untracked with dir rename/rename(1to2)' '
 	(
 		cd 10c &&
 
@@ -3145,7 +3145,7 @@ test_expect_success '10d-setup: Delete untracked with dir rename/rename(2to1)' '
 	)
 '
 
-test_expect_failure '10d-check: Delete untracked with dir rename/rename(2to1)' '
+test_expect_success '10d-check: Delete untracked with dir rename/rename(2to1)' '
 	(
 		cd 10d &&