README.md: expand overview

README.md

@@ -1,3 +1,5 @@
+[![Build Status](https://api.travis-ci.org/JehanneOS/jehanne.svg?branch=master)](https://travis-ci.org/JehanneOS/jehanne)
+
 # Jehanne
 
 Jehanne is a [simple][simplicity] operating system. 
@@ -7,10 +9,72 @@ It is a fork of [Harvey][harvey] (which in turn is a fork of
 diverges from the design and conventions of its ancestors whenever
 they are at odds with its goals.
 
-For this reason project is named after the famous Franch heretic [Joan of Arc][arc].  
+For this reason the project is named after the famous Franch heretic [Joan of Arc][arc].  
+
+## Overview
+
+This is the main repository, used to build the system as a whole:
+
+- [arch](./arch/) contains one folder for each
+  supported architecture, with specific C headers and binaries
+- [sys](./sys) is the system folder
+    * [include](./sys/include) contains portable C headers
+    * [lib](./sys/lib) contains data and scripts used by the 
+      running system
+    * [man](./sys/man) contains manual pages
+    * [src](./sys/src) contains the sources of the system
+- [doc](./doc/) contains useful documentation for Jehanne
+  development
+    * [license](./doc/license/) contains detailed info 
+      about Jehanne [licenses][lic]
+    * [hacking](./doc/hacking/) contains details about how
+      to build and modify Jehanne
+- [hacking](./hacking) contains the utilities used to
+  develop Jehanne
+- [qa](./qa) contains the regression tests
+- [mnt](./mnt) contains default mount targets
+- [usr](./usr) contains the users' folders
+- [pkgs](./pkgs) will contains the installed packages
+
+The running system also includes supplemental folders like `/lib`,
+`/bin` and `/dev` that are bound during the boot as required.
+
+## Build
+
+To build Jehanne and play with it, you need to have git, golang, qemu, 
+gcc, binutils and bison installed. 
+For example on Debian GNU/Linux you should be able to get going with
+
+	sudo aptitude install git golang build-essential bison qemu-system
+
+After the repository clone, you can give a look with
+
+	git submodule init			# we have a lot of submodules
+	git submodule update --init --recursive
+	./hacking/devshell.sh			# start a shell with appropriate environment
+	./hacking/continuous-build.sh		# to build everything
+	./hacking/runOver9P.sh			# to start the system in QEMU
+	./hacking/drawterm.sh			# to connect Jehanne with drawterm
+
+## Hacking
+
+Jehanne is a work in progress. 
+Forks and pull requests are welcome.
+
+In [doc/hacking](./doc/hacking/) you will find all you 
+need to know about its principles, design and weirdness.
+
+There's a lot of work to do, in every area of the system.
+
+To coordinate our efforts, we use the github issues.
+To discuss (and even debate) about the design and development of Jehanne
+we use the [JehanneOS mailing list][mailinglist]: please join and present
+yourself and your attitudes.
 
 [simplicity]: http://plato.stanford.edu/entries/simplicity/ "What is simplicity?"
 [harvey]: http://harvey-os.org "Harvey OS"
 [plan9]: https://github.com/brho/plan9 "UC Berkeley release of Plan 9 under the GPLv2"
 [nix]: https://github.com/rminnich/nix-os
 [arc]: https://en.wikipedia.org/wiki/Joan_of_Arc "Jeanne d'Arc"
+[lic]: ./LICENSE.md "A summary of Jehanne licensing"
+[mailinglist]: https://groups.google.com/forum/#!forum/jehanneos