Documentation: minor improvements

- link to OPAM2 rc2
- fix some broken links
- add x86_64 restriction for the installation scripts
- misc rephrasing.

docs/introduction/alphanet.rst

@@ -20,12 +20,13 @@ How to join the alphanet
 
 We provide two ways of joining the alphanet :
 
--  use ``docker`` and prebuilt binaries (recommended way, tested on
-   windows/mac/linux)
--  manual compilation and installation (linux and mac only)
+- an installation script that uses ``docker`` and prebuilt binaries
+  (recommended way, tested on windows/mac/linux, works on **x86_64**
+  architecture only),
+- manual compilation and installation (linux and mac only).
 
-The ``alphanet.sh`` script
-~~~~~~~~~~~~~~~~~~~~~~~~~~
+The ``alphanet.sh`` script (x86_64 only)
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 The recommended way for running an up-to-date Tezos node connected to
 the alphanet is to use ``scripts/alphanet.sh``. Its only requirement is
@@ -138,17 +139,11 @@ Please drink carefully and don't abuse the faucet: it only contains
 How to play with smart-contracts
 --------------------------------
 
-An advanced documentation of the smart contract language is in
+An advanced documentation of the smart contract language is available :ref:`here<michelson>`.
 
-``/docs/language.md``
+Some test contracts can be found in directory :src:`src/bin_client/test/contracts/`.
 
-Some test contracts are in
-
-``/tests/contracts/``
-
-For details and examples, see:
-
-https://www.michelson-lang.com/
+For details and examples, see also https://www.michelson-lang.com/
 
 How to bake on the alphanet
 ---------------------------

docs/introduction/howto.rst

@@ -23,7 +23,7 @@ You also need to **choose a branch**:
 
 ::
 
-   git clone git@gitlab.com:tezos/tezos.git
+   git clone https://gitlab.com/tezos/tezos.git
    git checkout alphanet
 
 Install OPAM
@@ -37,7 +37,7 @@ The simplest way to install all dependencies is by using `OPAM
 
 
 **IMPORTANT**: Please use `version 2
-<https://github.com/ocaml/opam/releases/tag/2.0.0-rc>`_ of OPAM. That
+<https://opam.ocaml.org/blog/opam-2-0-0-rc2/>`_ of OPAM. That
 is what the Tezos Core team uses. Most distribution probably ship
 **version 1** of OPAM out of the box, but installing version 2 is
 preferable for many reasons.
@@ -219,7 +219,7 @@ To interact with your node, read the doc of clients:
    ./tezos-admin-client man
    ./tezos-alpha-baker man
 
-And read :ref:`this page<alphanet>` to get alphanet tezzies.
+And read :ref:`this section<faucet>` to learn how to get alphanet tezzies.
 
 Use sandboxed mode
 ------------------

docs/whitedoc/michelson.rst

@@ -1,3 +1,5 @@
+.. _michelson:
+
 Michelson: the language of Smart Contracts in Tezos
 ===================================================