[PATCH v4 07/10] attr: be careful about sparse directories

["Derrick Stolee via GitGitGadget" <gitgitgadget@gmail.com>]

From: Derrick Stolee <dstolee@microsoft.com>

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
---
 attr.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/attr.c b/attr.c
index d029e681f28..62db4aed443 100644
--- a/attr.c
+++ b/attr.c
@@ -14,6 +14,7 @@
 #include "utf8.h"
 #include "quote.h"
 #include "thread-utils.h"
+#include "dir.h"
 
 const char git_attr__true[] = "(builtin)true";
 const char git_attr__false[] = "\0(builtin)false";
@@ -744,6 +745,19 @@ static struct attr_stack *read_attr_from_index(struct index_state *istate,
 	if (!istate)
 		return NULL;
 
+	/*
+	 * The .gitattributes file only applies to files within its
+	 * parent directory. In the case of cone-mode sparse-checkout,
+	 * the .gitattributes file is sparse if and only if all paths
+	 * within that directory are also sparse. Thus, don't load the
+	 * .gitattributes file since it will not matter.
+	 *
+	 * In the case of a sparse index, it is critical that we don't go
+	 * looking for a .gitattributes file, as the index will expand.
+	 */
+	if (!path_in_cone_mode_sparse_checkout(path, istate))
+		return NULL;
+
 	buf = read_blob_data_from_index(istate, path, NULL);
 	if (!buf)
 		return NULL;
-- 
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