Merge pull request git-for-windows#473: Sparse Index: fix a checkout …

…bug with deep sparse-checkout paths

We got multiple similar reports of failures with the sparse index (git-for-windows#473 as an issue, and another regarding `git checkout` via email). Both were hitting a similar set of paths, which was a hint.

The reason we didn't hit this before is because it requires the following:

1. The sparse-checkout definition needs to have recursive inclusion of deep folders (depth 3 or more).
2. _Adjacent_ to those deep folders, we need a deep sparse directory entry that receives changes.
3. In this particular repo, deep directories are only added to the sparse-checkout in rare occasions and those adjacent folders are rarely updated. They happened to update this week and hit our sparse index dogfooders in surprising ways.

The first commit adds a test that fails without the fix. It requires modifying our test data to make adjacent, deep sparse directory entries possible. It's a rather simple test after we have that data change.

The second commit includes the actual fix. It's really just an error of not understanding the difference between the `name` and `traverse_path` members of the `struct traverse_info` structure. `name` only stores a single tree entry while `traverse_path` actually includes the full name from root. The method we are editing also has an additional `struct name_entry` that fills in the tree entry on top of the `traverse_path`, which explains how this worked to depth two, but not depth three.

Resolves git-for-windows#473 
See also gitgitgadget#1092

t/t1092-sparse-checkout-compatibility.sh

@@ -19,6 +19,8 @@ test_expect_success 'setup' '
 		mkdir folder1 folder2 deep x &&
 		mkdir deep/deeper1 deep/deeper2 deep/before deep/later &&
 		mkdir deep/deeper1/deepest &&
+		mkdir deep/deeper1/deepest2 &&
+		mkdir deep/deeper1/deepest3 &&
 		echo "after deeper1" >deep/e &&
 		echo "after deepest" >deep/deeper1/e &&
 		cp a folder1 &&
@@ -30,7 +32,9 @@ test_expect_success 'setup' '
 		cp a deep/deeper2 &&
 		cp a deep/later &&
 		cp a deep/deeper1/deepest &&
-		cp -r deep/deeper1/deepest deep/deeper2 &&
+		cp a deep/deeper1/deepest2 &&
+		cp a deep/deeper1/deepest3 &&
+		cp -r deep/deeper1/ deep/deeper2 &&
 		mkdir deep/deeper1/0 &&
 		mkdir deep/deeper1/0/0 &&
 		touch deep/deeper1/0/1 &&
@@ -126,6 +130,8 @@ test_expect_success 'setup' '
 
 		git checkout -b deepest base &&
 		echo "updated deepest" >deep/deeper1/deepest/a &&
+		echo "updated deepest2" >deep/deeper1/deepest2/a &&
+		echo "updated deepest3" >deep/deeper1/deepest3/a &&
 		git commit -a -m "update deepest" &&
 
 		git checkout -f base &&
@@ -302,6 +308,14 @@ test_expect_success 'add, commit, checkout' '
 	test_all_match git checkout -
 '
 
+test_expect_success 'deep changes during checkout' '
+	init_repos &&
+
+	test_sparse_match git sparse-checkout set deep/deeper1/deepest &&
+	test_all_match git checkout deepest &&
+	test_all_match git checkout base
+'
+
 test_expect_success 'add outside sparse cone' '
 	init_repos &&
 

unpack-trees.c

@@ -1258,7 +1258,9 @@ static int find_cache_pos(struct traverse_info *info,
 
 /*
  * Given a sparse directory entry 'ce', compare ce->name to
- * info->name + '/' + p->path + '/' if info->name is non-empty.
+ * info->traverse_path + p->path + '/' if info->traverse_path
+ * is non-empty.
+ *
  * Compare ce->name to p->path + '/' otherwise. Note that
  * ce->name must end in a trailing '/' because it is a sparse
  * directory entry.
@@ -1270,11 +1272,11 @@ static int sparse_dir_matches_path(const struct cache_entry *ce,
 	assert(S_ISSPARSEDIR(ce->ce_mode));
 	assert(ce->name[ce->ce_namelen - 1] == '/');
 
-	if (info->namelen)
-		return ce->ce_namelen == info->namelen + p->pathlen + 2 &&
-		       ce->name[info->namelen] == '/' &&
-		       !strncmp(ce->name, info->name, info->namelen) &&
-		       !strncmp(ce->name + info->namelen + 1, p->path, p->pathlen);
+	if (info->pathlen)
+		return ce->ce_namelen == info->pathlen + p->pathlen + 1 &&
+		       ce->name[info->pathlen - 1] == '/' &&
+		       !strncmp(ce->name, info->traverse_path, info->pathlen) &&
+		       !strncmp(ce->name + info->pathlen, p->path, p->pathlen);
 	return ce->ce_namelen == p->pathlen + 1 &&
 	       !strncmp(ce->name, p->path, p->pathlen);
 }