Give the correct name for the function in the doc. Per @carlosmn, git_index_add is now named git_index_add_bypath.
diff --git a/include/git2/index.h b/include/git2/index.h
index dad4234..9a7ad28 100644
--- a/include/git2/index.h
+++ b/include/git2/index.h
@@ -158,8 +158,8 @@ typedef enum {
* to back it.
*
* Since there is no ODB or working directory behind this index,
- * any Index methods which rely on these (e.g. index_add) will
- * fail with the GIT_ERROR error code.
+ * any Index methods which rely on these (e.g. index_add_bypath)
+ * will fail with the GIT_ERROR error code.
*
* If you need to access the index of an actual repository,
* use the `git_repository_index` wrapper.