From 4f35ebab20f1034df1df943044903e7044e6cdf4 Mon Sep 17 00:00:00 2001
From: Paulo Gomes <pjbgf@linux.com>
Date: Sun, 13 Apr 2025 16:48:21 +0100
Subject: [PATCH] Merge pull request #1484 from patricsss/patricsss/fix-1455

utils: fix diff so subpaths work for sparse checkouts, fixes 1455
---
 utils/merkletrie/change.go          |  2 +-
 utils/merkletrie/index/node.go      | 10 ++++++++-
 utils/merkletrie/index/node_test.go | 34 +++++++++++++++++++++++++----
 3 files changed, 40 insertions(+), 6 deletions(-)

diff --git a/utils/merkletrie/change.go b/utils/merkletrie/change.go
index 562ff8902..d32b5a7d4 100644
--- a/utils/merkletrie/change.go
+++ b/utils/merkletrie/change.go
@@ -150,7 +150,7 @@ func (l *Changes) addRecursive(root noder.Path, ctor noderToChangeFn) error {
 			}
 			return err
 		}
-		if current.IsDir() {
+		if current.IsDir() || current.Skip() {
 			continue
 		}
 		l.Add(ctor(current))
diff --git a/utils/merkletrie/index/node.go b/utils/merkletrie/index/node.go
index c1809f7ec..5bc63f8b2 100644
--- a/utils/merkletrie/index/node.go
+++ b/utils/merkletrie/index/node.go
@@ -36,7 +36,15 @@ func NewRootNode(idx *index.Index) noder.Noder {
 			parent := fullpath
 			fullpath = path.Join(fullpath, part)
 
-			if _, ok := m[fullpath]; ok {
+			// It's possible that the first occurrence of subdirectory is skipped.
+			// The parent node can be created with SkipWorktree set to true, but
+			// if any future children do not skip their subtree, the entire lineage
+			// of the tree needs to have this value set to false so that subdirectories
+			// are not ignored.
+			if parentNode, ok := m[fullpath]; ok {
+				if e.SkipWorktree == false {
+					parentNode.skip = false
+				}
 				continue
 			}
 
diff --git a/utils/merkletrie/index/node_test.go b/utils/merkletrie/index/node_test.go
index cc5600dcb..53f8a9f45 100644
--- a/utils/merkletrie/index/node_test.go
+++ b/utils/merkletrie/index/node_test.go
@@ -2,7 +2,7 @@ package index
 
 import (
 	"bytes"
-	"path/filepath"
+	"path"
 	"testing"
 
 	"github.com/go-git/go-git/v5/plumbing"
@@ -46,14 +46,14 @@ func (s *NoderSuite) TestDiff(c *C) {
 func (s *NoderSuite) TestDiffChange(c *C) {
 	indexA := &index.Index{
 		Entries: []*index.Entry{{
-			Name: filepath.Join("bar", "baz", "bar"),
+			Name: path.Join("bar", "baz", "bar"),
 			Hash: plumbing.NewHash("8ab686eafeb1f44702738c8b0f24f2567c36da6d"),
 		}},
 	}
 
 	indexB := &index.Index{
 		Entries: []*index.Entry{{
-			Name: filepath.Join("bar", "baz", "foo"),
+			Name: path.Join("bar", "baz", "foo"),
 			Hash: plumbing.NewHash("8ab686eafeb1f44702738c8b0f24f2567c36da6d"),
 		}},
 	}
@@ -63,6 +63,32 @@ func (s *NoderSuite) TestDiffChange(c *C) {
 	c.Assert(ch, HasLen, 2)
 }
 
+func (s *NoderSuite) TestDiffSkipIssue1455(c *C) {
+	indexA := &index.Index{
+		Entries: []*index.Entry{
+			{
+				Name:         path.Join("bar", "baz", "bar"),
+				Hash:         plumbing.NewHash("8ab686eafeb1f44702738c8b0f24f2567c36da6d"),
+				SkipWorktree: true,
+			},
+			{
+				Name:         path.Join("bar", "biz", "bat"),
+				Hash:         plumbing.NewHash("8ab686eafeb1f44702738c8b0f24f2567c36da6d"),
+				SkipWorktree: false,
+			},
+		},
+	}
+
+	indexB := &index.Index{}
+
+	ch, err := merkletrie.DiffTree(NewRootNode(indexB), NewRootNode(indexA), isEquals)
+	c.Assert(err, IsNil)
+	c.Assert(ch, HasLen, 1)
+	a, err := ch[0].Action()
+	c.Assert(err, IsNil)
+	c.Assert(a, Equals, merkletrie.Insert)
+}
+
 func (s *NoderSuite) TestDiffDir(c *C) {
 	indexA := &index.Index{
 		Entries: []*index.Entry{{
@@ -73,7 +99,7 @@ func (s *NoderSuite) TestDiffDir(c *C) {
 
 	indexB := &index.Index{
 		Entries: []*index.Entry{{
-			Name: filepath.Join("foo", "bar"),
+			Name: path.Join("foo", "bar"),
 			Hash: plumbing.NewHash("8ab686eafeb1f44702738c8b0f24f2567c36da6d"),
 		}},
 	}