Initial commit of the README

Author: hlinnaka

README.md

@@ -0,0 +1,16 @@
+This repository holds Neon-specific changes to PostgreSQL
+sources. This main branch is a dummy and only contains this
+README. The active branches are:
+
+- [REL_17_STABLE_neon](https://github.com/neondatabase/postgres/tree/REL_17_STABLE_neon)
+- [REL_16_STABLE_neon](https://github.com/neondatabase/postgres/tree/REL_16_STABLE_neon)
+- [REL_15_STABLE_neon](https://github.com/neondatabase/postgres/tree/REL_15_STABLE_neon)
+- [REL_14_STABLE_neon](https://github.com/neondatabase/postgres/tree/REL_14_STABLE_neon)
+
+These branches are submodules in the main
+[neon](https://github.com/neondatabase/neon) repository under
+`vendor/postgres-*`. There's not much point in cloning this repository
+independently.
+
+List of the changes compared to upstream PostgreSQL can be found at
+https://github.com/neondatabase/neon/blob/main/docs/core_changes.md.