[PATCH v2 6/8] 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..a1009f78029 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;
 
+	/*
+	 * In the case of cone-mode sparse-checkout, getting the
+	 * .gitattributes file from a directory is meaningless: all
+	 * contained paths will be sparse if the .gitattributes is also
+	 * sparse. In the case of a sparse index, it is critical that we
+	 * don't go looking for one as it will expand the index.
+	 */
+	init_sparse_checkout_patterns(istate);
+	if (istate->sparse_checkout_patterns &&
+	    istate->sparse_checkout_patterns->use_cone_patterns &&
+	    path_in_sparse_checkout(path, istate) == NOT_MATCHED)
+		return NULL;
+
 	buf = read_blob_data_from_index(istate, path, NULL);
 	if (!buf)
 		return NULL;
-- 
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