1 files changed, 43 insertions, 15 deletions

diff --git a/sparse-index.c b/sparse-index.c
index 7b7ff79e04..a1d505d50e 100644
--- a/sparse-index.c
+++ b/sparse-index.c
@@ -122,17 +122,17 @@ static int index_has_unmerged_entries(struct index_state *istate)
 	return 0;
 }
 
-int convert_to_sparse(struct index_state *istate, int flags)
+static int is_sparse_index_allowed(struct index_state *istate, int flags)
 {
-	int test_env;
-	if (istate->sparse_index || !istate->cache_nr ||
-	    !core_apply_sparse_checkout || !core_sparse_checkout_cone)
+	if (!core_apply_sparse_checkout || !core_sparse_checkout_cone)
 		return 0;
 
 	if (!istate->repo)
 		istate->repo = the_repository;
 
 	if (!(flags & SPARSE_INDEX_MEMORY_ONLY)) {
+		int test_env;
+
 		/*
 		 * The sparse index is not (yet) integrated with a split index.
 		 */
@@ -168,25 +168,41 @@ int convert_to_sparse(struct index_state *istate, int flags)
 	if (!istate->sparse_checkout_patterns->use_cone_patterns)
 		return 0;
 
+	return 1;
+}
+
+int convert_to_sparse(struct index_state *istate, int flags)
+{
 	/*
-	 * NEEDSWORK: If we have unmerged entries, then stay full.
-	 * Unmerged entries prevent the cache-tree extension from working.
+	 * If the index is already sparse, empty, or otherwise
+	 * cannot be converted to sparse, do not convert.
 	 */
-	if (index_has_unmerged_entries(istate))
+	if (istate->sparse_index || !istate->cache_nr ||
+	    !is_sparse_index_allowed(istate, flags))
 		return 0;
 
-	/* Clear and recompute the cache-tree */
-	cache_tree_free(&istate->cache_tree);
 	/*
-	 * Silently return if there is a problem with the cache tree update,
-	 * which might just be due to a conflict state in some entry.
-	 *
-	 * This might create new tree objects, so be sure to use
-	 * WRITE_TREE_MISSING_OK.
+	 * NEEDSWORK: If we have unmerged entries, then stay full.
+	 * Unmerged entries prevent the cache-tree extension from working.
 	 */
-	if (cache_tree_update(istate, WRITE_TREE_MISSING_OK))
+	if (index_has_unmerged_entries(istate))
 		return 0;
 
+	if (!cache_tree_fully_valid(istate->cache_tree)) {
+		/* Clear and recompute the cache-tree */
+		cache_tree_free(&istate->cache_tree);
+
+		/*
+		 * Silently return if there is a problem with the cache tree update,
+		 * which might just be due to a conflict state in some entry.
+		 *
+		 * This might create new tree objects, so be sure to use
+		 * WRITE_TREE_MISSING_OK.
+		 */
+		if (cache_tree_update(istate, WRITE_TREE_MISSING_OK))
+			return 0;
+	}
+
 	remove_fsmonitor(istate);
 
 	trace2_region_enter("index", "convert_to_sparse", istate->repo);
@@ -313,6 +329,18 @@ void ensure_full_index(struct index_state *istate)
 	trace2_region_leave("index", "ensure_full_index", istate->repo);
 }
 
+void ensure_correct_sparsity(struct index_state *istate)
+{
+	/*
+	 * If the index can be sparse, make it sparse. Otherwise,
+	 * ensure the index is full.
+	 */
+	if (is_sparse_index_allowed(istate, 0))
+		convert_to_sparse(istate, 0);
+	else
+		ensure_full_index(istate);
+}
+
 /*
  * This static global helps avoid infinite recursion between
  * expand_to_path() and index_file_exists().