sparse-checkout: create helper methods

As we integrate the sparse index into more builtins, we occasionally
need to check the sparse-checkout patterns to see if a path is within
the sparse-checkout cone. Create some helper methods that help
initialize the patterns and check for pattern matching to make this
easier.

The existing callers of commands like get_sparse_checkout_patterns() use
a custom 'struct pattern_list' that is not necessarily the one in the
'struct index_state', so there are not many previous uses that could
adopt these helpers. There are just two in builtin/add.c and
sparse-index.c that can use path_in_sparse_checkout().

We add a path_in_cone_mode_sparse_checkout() as well that will only
return false if the path is outside of the sparse-checkout definition
_and_ the sparse-checkout patterns are in cone mode.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>

builtin/add.c

@@ -190,21 +190,16 @@ static int refresh(int verbose, const struct pathspec *pathspec)
 	struct string_list only_match_skip_worktree = STRING_LIST_INIT_NODUP;
 	int flags = REFRESH_IGNORE_SKIP_WORKTREE |
 		    (verbose ? REFRESH_IN_PORCELAIN : REFRESH_QUIET);
-	struct pattern_list pl = { 0 };
-	int sparse_checkout_enabled = !get_sparse_checkout_patterns(&pl);
 
 	seen = xcalloc(pathspec->nr, 1);
 	refresh_index(&the_index, flags, pathspec, seen,
 		      _("Unstaged changes after refreshing the index:"));
 	for (i = 0; i < pathspec->nr; i++) {
 		if (!seen[i]) {
 			const char *path = pathspec->items[i].original;
-			int dtype = DT_REG;
 
 			if (matches_skip_worktree(pathspec, i, &skip_worktree_seen) ||
-			    (sparse_checkout_enabled &&
-			     !path_matches_pattern_list(path, strlen(path), NULL,
-							&dtype, &pl, &the_index))) {
+			    !path_in_sparse_checkout(path, &the_index)) {
 				string_list_append(&only_match_skip_worktree,
 						   pathspec->items[i].original);
 			} else {

dir.c

@@ -1439,6 +1439,60 @@ enum pattern_match_result path_matches_pattern_list(
 	return result;
 }
 
+int init_sparse_checkout_patterns(struct index_state *istate)
+{
+	if (!core_apply_sparse_checkout ||
+	    istate->sparse_checkout_patterns)
+		return 0;
+
+	CALLOC_ARRAY(istate->sparse_checkout_patterns, 1);
+
+	if (get_sparse_checkout_patterns(istate->sparse_checkout_patterns) < 0) {
+		FREE_AND_NULL(istate->sparse_checkout_patterns);
+		return -1;
+	}
+
+	return 0;
+}
+
+static int path_in_sparse_checkout_1(const char *path,
+				     struct index_state *istate,
+				     int require_cone_mode)
+{
+	const char *base;
+	int dtype = DT_REG;
+	init_sparse_checkout_patterns(istate);
+
+	/*
+	 * We default to accepting a path if there are no patterns or
+	 * they are of the wrong type.
+	 */
+	if (!istate->sparse_checkout_patterns ||
+	    (require_cone_mode &&
+	     !istate->sparse_checkout_patterns->use_cone_patterns))
+		return 1;
+
+
+
+	base = strrchr(path, '/');
+	return path_matches_pattern_list(path, strlen(path), base ? base + 1 : path,
+					 &dtype,
+					 istate->sparse_checkout_patterns,
+					 istate) > 0;
+}
+
+int path_in_sparse_checkout(const char *path,
+			    struct index_state *istate)
+{
+	return path_in_sparse_checkout_1(path, istate, 0);
+}
+
+int path_in_cone_modesparse_checkout(const char *path,
+				     struct index_state *istate)
+{
+	return path_in_sparse_checkout_1(path, istate, 1);
+}
+
 static struct path_pattern *last_matching_pattern_from_lists(
 		struct dir_struct *dir, struct index_state *istate,
 		const char *pathname, int pathlen,

dir.h

@@ -394,6 +394,14 @@ enum pattern_match_result path_matches_pattern_list(const char *pathname,
 				const char *basename, int *dtype,
 				struct pattern_list *pl,
 				struct index_state *istate);
+
+int init_sparse_checkout_patterns(struct index_state *state);
+
+int path_in_sparse_checkout(const char *path,
+			    struct index_state *istate);
+int path_in_cone_modesparse_checkout(const char *path,
+				     struct index_state *istate);
+
 struct dir_entry *dir_add_ignored(struct dir_struct *dir,
 				  struct index_state *istate,
 				  const char *pathname, int len);

sparse-index.c

@@ -34,17 +34,14 @@ static int convert_to_sparse_rec(struct index_state *istate,
 	int i, can_convert = 1;
 	int start_converted = num_converted;
 	enum pattern_match_result match;
-	int dtype = DT_UNKNOWN;
 	struct strbuf child_path = STRBUF_INIT;
-	struct pattern_list *pl = istate->sparse_checkout_patterns;
 
 	/*
 	 * Is the current path outside of the sparse cone?
 	 * Then check if the region can be replaced by a sparse
 	 * directory entry (everything is sparse and merged).
 	 */
-	match = path_matches_pattern_list(ct_path, ct_pathlen,
-					  NULL, &dtype, pl, istate);
+	match = path_in_sparse_checkout(ct_path, istate);
 	if (match != NOT_MATCHED)
 		can_convert = 0;
 
@@ -153,11 +150,8 @@ int convert_to_sparse(struct index_state *istate)
 	if (!istate->repo->settings.sparse_index)
 		return 0;
 
-	if (!istate->sparse_checkout_patterns) {
-		istate->sparse_checkout_patterns = xcalloc(1, sizeof(struct pattern_list));
-		if (get_sparse_checkout_patterns(istate->sparse_checkout_patterns) < 0)
-			return 0;
-	}
+	if (init_sparse_checkout_patterns(istate) < 0)
+		return 0;
 
 	/*
 	 * We need cone-mode patterns to use sparse-index. If a user edits