Update README

README.md

@@ -30,6 +30,31 @@ GF particularly addresses four aspects of grammars:
 - grammar engineering (modularity, abstractions, libraries)
 - embeddability in programs written in other languages (C, C++, Haskell, Java, JavaScript)
 
-COMPILATION and INSTALLATION of source distribution:
-See [download/index.html](download/index.html) for installation instructions.
-More details can be found in [doc/gf-developers.html](doc/gf-developers.html).
+## Compilation and installation
+
+The simplest way of installing GF is with the command:
+```
+cabal install
+```
+
+This can be broken down into the usual sub-steps:
+```
+cabal configure
+cabal build
+cabal copy
+```
+
+For more details, see the [download page](http://www.grammaticalframework.org/download/index.html)
+and [developers manual](http://www.grammaticalframework.org/doc/gf-developers.html).
+
+## About this repository
+
+On 2018-07-25, the monolithic [GF repository](https://github.com/GrammaticalFramework/GF)
+was split in two:
+
+1. [gf-core](https://github.com/GrammaticalFramework/gf-core) —  the GF compiler, shell and runtimes
+2. [gf-rgl](https://github.com/GrammaticalFramework/gf-rgl) — the resource grammar library
+
+The former repository is now archived and no longer updated.
+The split was performed using [this script](https://github.com/GrammaticalFramework/GF/blob/30ae1b5a5f73513ac5825ca6712186ef8afe9fd4/split/run.sh)
+and the output of that script is [here](https://gist.github.com/johnjcamilleri/a6c43ff61f15a9657b457ac94ab7db61).