Bumping version format. (#1640)

The docstore format has changed in a non-compatible manner.

Author: fulmicoton

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "tantivy"
-version = "0.18.1"
+version = "0.19.0-dev"
 authors = ["Paul Masurel <[email protected]>"]
 license = "MIT"
 categories = ["database-implementations", "data-structures"]

src/lib.rs

@@ -311,7 +311,7 @@ pub use crate::postings::Postings;
 pub use crate::schema::{DateOptions, DatePrecision, Document, Term};
 
 /// Index format version.
-const INDEX_FORMAT_VERSION: u32 = 4;
+const INDEX_FORMAT_VERSION: u32 = 5;
 
 /// Structure version for the index.
 #[derive(Clone, PartialEq, Eq, Serialize, Deserialize)]