Introduced in Git 2.18, Git wire protocol version 2 is now used by default in Git latest version, 2.26. Git 2.26 also improves configuration option handling and sparse-checkouts, among other things.
Git’s wire protocol defines how Git clients and servers communicate with each other. The new Git protocol version improves performance by enabling server-side filtering of references, which include not only branches and tags but also, e.g., pull request heads and others. Clients adopting Git protocol version 2 will be able to specify which references they are interested in, thus reducing the amount of data the server sends back.
