repository: add index_state to struct repo

Signed-off-by: Brandon Williams <bmwill@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

repository.c

@@ -163,4 +163,20 @@ void repo_clear(struct repository *repo)
 		free(repo->config);
 		repo->config = NULL;
 	}
+
+	if (repo->index) {
+		discard_index(repo->index);
+		free(repo->index);
+		repo->index = NULL;
+	}
+}
+
+int repo_read_index(struct repository *repo)
+{
+	if (!repo->index)
+		repo->index = xcalloc(1, sizeof(*repo->index));
+	else
+		discard_index(repo->index);
+
+	return read_index_from(repo->index, repo->index_file);
 }

repository.h

@@ -2,6 +2,7 @@
 #define REPOSITORY_H
 
 struct config_set;
+struct index_state;
 
 struct repository {
 	/* Environment */
@@ -49,6 +50,12 @@ struct repository {
 	 */
 	struct config_set *config;
 
+	/*
+	 * Repository's in-memory index.
+	 * 'repo_read_index()' can be used to populate 'index'.
+	 */
+	struct index_state *index;
+
 	/* Configurations */
 	/*
 	 * Bit used during initialization to indicate if repository state (like
@@ -71,4 +78,6 @@ extern void repo_set_worktree(struct repository *repo, const char *path);
 extern int repo_init(struct repository *repo, const char *gitdir, const char *worktree);
 extern void repo_clear(struct repository *repo);
 
+extern int repo_read_index(struct repository *repo);
+
 #endif /* REPOSITORY_H */