Creating and using a git mirror
'''''''''''''''''''''''''''''''
This is an example of how to create a git mirror using git's
`git-http-backend <https://git-scm.com/docs/git-http-backend>`_ and
`lighttpd <https://redmine.lighttpd.net/projects/1/wiki/TutorialConfiguration>`_.


Prerequisites
=============
You will need git installed, and git-http-backend must be present. It is assumed
that the git-http-backend binary exists at `/usr/lib/git-core/git-http-backend`.

You will need `lighttpd` installed, and at the bare minimum has the modules
`mod_alias`, `mod_cgi`, and `mod_setenv`.

I will be using gnome-modulesets as an example, which can be cloned from
`http://gnome7.codethink.co.uk/gnome-modulesets.git`.


Starting a git http server
==========================


1. Set up a directory containing mirrors
----------------------------------------
Choose a suitable directory to hold your mirrors, e.g. `/var/www/git`.

Place the git repositories you want to use as mirrors in the mirror dir, e.g.
``git clone --mirror http://git.gnome.org/browse/yelp-xsl /var/www/git/yelp-xsl.git``.


2. Configure lighttpd
---------------------
Write out a lighttpd.conf as follows:

::

   server.document-root = "/var/www/git/" 
   server.port = 3000
   server.modules = (
        "mod_alias",
        "mod_cgi",
        "mod_setenv",
   )
   
   alias.url += ( "/git" => "/usr/lib/git-core/git-http-backend" )
   $HTTP["url"] =~ "^/git" {
        cgi.assign = ("" => "")
        setenv.add-environment = (
                "GIT_PROJECT_ROOT" => "/var/www/git",
                "GIT_HTTP_EXPORT_ALL" => ""
        )
   }

.. note::

   If you have your mirrors in another directory, replace /var/www/git/ with that directory.


3. Start lighttpd
-----------------
lighttpd can be invoked with the command-line ``lighttpd -D -f lighttpd.conf``.


4. Test that you can fetch from it
----------------------------------
We can then clone the mirrored repo using git via http with
``git clone http://127.0.0.1:3000/git/yelp-xsl``.

.. note::

   If you have set server.port to something other than the default, you will
   need to replace the '3000' in the command-line.


5. Configure the project to use the mirror
------------------------------------------
To add this local http server as a mirror, add the following to the project.conf:

.. code:: yaml

   mirrors:
   - name: local-mirror
     aliases:
       git_gnome_org:
       - http://127.0.0.1:3000/git/


6. Test that the mirror works
-----------------------------
We can make buildstream use the mirror by setting the alias to an invalid URL, e.g.

.. code:: yaml

   aliases:
     git_gnome_org: https://www.example.com/invalid/url/

Now, if you build an element that uses the source you placed in the mirror
(e.g. ``bst build core-deps/yelp-xsl.bst``), you will see that it uses your mirror.


.. _lighttpd_git_tar_conf:

Bonus: lighttpd conf for git and tar
====================================
For those who have also used the :ref:`tar-mirror tutorial <using_tar_mirror>`,
a combined lighttpd.conf is below:

::

   server.document-root = "/var/www/"
   server.port = 3000
   server.modules = (
           "mod_alias",
           "mod_cgi",
           "mod_setenv",
   )
   
   alias.url += ( "/git" => "/usr/lib/git-core/git-http-backend" )
   $HTTP["url"] =~ "^/git" {
           cgi.assign = ("" => "")
           setenv.add-environment = (
                   "GIT_PROJECT_ROOT" => "/var/www/git",
                   "GIT_HTTP_EXPORT_ALL" => ""
           )
   } else $HTTP["url"] =~ "^/tar" {
           dir-listing.activate = "enable"
   }


Further reading
===============
If this mirror isn't being used exclusively in a secure network, it is strongly
recommended you `use SSL <https://redmine.lighttpd.net/projects/1/wiki/HowToSimpleSSL>`_.

This is the bare minimum required to set up a git mirror. A large, public project
would prefer to set it up using the
`git protocol <https://git-scm.com/book/en/v1/Git-on-the-Server-Git-Daemon>`_,
and a security-conscious project would be configured to use
`git over SSH <https://git-scm.com/book/en/v1/Git-on-the-Server-Getting-Git-on-a-Server#Small-Setups>`_.

Lighttpd is documented on `its wiki <https://redmine.lighttpd.net/projects/lighttpd/wiki>`_.