Obsolete:Tutorial on using git in Moodle development

Revision as of 19:27, 26 October 2009 by David Mudrak (talk | contribs) (Branching a plugin from CONTRIB)

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Note: You are currently viewing documentation for Moodle 1.9. Up-to-date documentation for the latest stable version is available here: Tutorial on using git in Moodle development.

Disclaimer: This is not a tutorial on git itself. You are supposed to know the basic concepts of git (notably cloning, branching and merging). This tutorial is based on my personal experience with using git in Moodle development process. There are other (and almost certainly better) ways of doing it. See the references at the bottom of the page. Quite often, I found a solution that just worked and did not explore alternatives. You are warmly welcome to contribute and improve this tutorial. Please use the talk page to add/fix something so I can merge it into the tutorial text. --David Mudrak

Preparing the environment

Set-up of servers used in this tutorial

In this tutorial, we will use the following environment. Check the diagram. At the moment, there are two source code repositories you can use: the main Moodle CVS server cvs.moodle.org and its git mirror at git.moodle.org. While the CVS contains both Moodle core code and the contributed code, the git mirrors the core code only yet (this may be changed in the near future). We also expect you have some server (we will call it "nostromo") that you and your team members use and that you do the actual developing at the localhost machines.

Later in this tutorial, you will see how

  • git fetch
    can be used to get the recent changes from upstream to nostromo
  • git cvsimport
    can be used to create your own git mirror of a contributed code (we do not do this yet for you)
  • git clone
    can be used to create a mirror of your nostromo repos at you local machines
  • git push
    can be used to backup your own work and to share it with your friend
  • git pull
    can be used regularly to fetch and merge the work done by your friend
  • git cvsexportcommit
    can be used to send your commits for the upstream (and you will, right? ;-)

Create your own Moodle source codes mirror

Make sure you and your team friends have write access to
/pub/scm/git
at your nostromo server.
$ ssh nostromo
$ cd /pub/scm/git
$ mkdir moodle.git
$ cd moodle.git
$ git init --bare

That will create an empty bare repository in /pub/scm/git/moodle.git directory. Shortly, the "bare" means it contains just the repository itself, not the working copy (checkout) of the files.

$ git --bare fetch git://git.moodle.org/moodle.git cvshead:cvshead
$ git --bare fetch git://git.moodle.org/moodle.git MOODLE_19_STABLE:MOODLE_19_STABLE
$ git --bare fetch git://git.moodle.org/moodle.git MOODLE_18_STABLE:MOODLE_18_STABLE

These three commands will create three branches - cvshead, MOODLE_19_STABLE and MOODLE_18_STABLE from the upstream and will fetch all the Moodle development history. You can re-run the same commands later to fetch the recent changes. They can be run by cron to regularly fetch the latest changes from the upstream to your nostromo repository. It makes sense to run theme every 30 minutes as it is the interval of the git.moodle.org updates.

Check out the working copies of the repository

Now let us go to your localhost machine and check out the working copy from the nostromo repository

$ cd ~/public_html
$ git clone ssh+git://nostromo/pub/scm/git/moodle.git moodle19
$ cd moodle19
$ git checkout -b MOODLE_19_STABLE origin/MOODLE_19_STABLE
After these commands, you have a checkout of the latest 1.9.x Moodle branch in your
~/public_html/moodle19
. To update it (it est to fetch the changes from your nostromo and to merge them), just run
$ git pull

Prepare a customized branch for your client

Imagine your are going to install and customize Moodle 1.9 for a client, for example the Hogwarts School. Let us create a branch for them where the whole customization will be done.

$ cd ~/public_html/moodle19
$ git checkout -b mdl19-hogwarts origin/MOODLE_19_STABLE
$ ... (do all your customization here, git add, git commit etc)

Now, publish your changes to nostromo so your friend can clone it. Also, pushing your stuff to a server is quite a good backup of your work.

$ git push origin mdl19-hogwarts:mdl19-hogwarts
Later on, just
git push
should be enough as the remote branch already exists but this depends on your git settings.

Your friend can make their own clone of your customizations with

$ cd ~/public_html/moodle19
$ git checkout -b mdl19-hogwarts origin/mdl19-hogwarts
$ ... (hack something, git add, git commit)
$ git push

Deploying a customized branch

With a shell access to the client's webhost

If you can, install git at the client's webhost. Then you can just create another clone of your customer's branch using the same commands as when you did during the checking out to your development machine.

With FTP access only

$ cd ~/public_html/moodle19
$ git checkout mdl19-hogwarts
$ git pull
$ git tag mdl19-hogwarts-20091026
$ git archive --format=tar --prefix=hogwarts/htdocs/ mdl19-hogwarts-20091026 | (cd /tmp/ && tar xf -)
Now you can upload
/tmp/hogwarts/htdocs/
to the server

Sending a single patch upstream

To be able to export patch from git and to commit it into CVS, you will need two Moodle checkouts - the git one and the CVS one. Let us say you have a local git clone in
~/public_html/moodlehead
and a pure CVS checkout of HEAD at
~/cvs/moodlehead
. Firstly, let us prepare some helpers.
$ cd ~/public_html/moodlehead
$ git config cvsexportcommit.cvsdir ~/cvs/moodlehead
$ git config --global alias.cvsupstream 'cvsexportcommit -c -p -u -v'

We just said git where to look for the CVS version of the repository (so it is not needed to type it every time) and created an alias for cvsexportcommit command with some parameters (RTFM). Now, let us go to fix and commit a bug:

$ git checkout -b somenastybug
$ ... (edit, git add, git commit - this leads to commit eg 3d9779d
$ git cvsupstream 3d9779d

The git commit will be re-applied to the CVS working copy and then committed to cvs.moodle.org as if you did it manually. It will be mirrored to git.moodle.org, fetched by nostromo and pulled back to your machine. When that happens, the command

$ git cherry cvshead

shall inform you that all commits from the current branch are already included in cvshead - it est, there are no cherries. So, you can delete the local bug branch:

$ git branch -D somenastybug
Please note, the commit id of your patch will be different in your fix branch and in the branch coming from CVS. That is why you need to use
git cherry
which compares the content of the patch.

Sending whole branch into CVS

Imagine you start to implement some new feature or you are rewriting/extending some subsystem. Let us say you decide to replace the underlying QuickForms library with a new and better framework (yay! kudos for you then :-)). As it is common with git, you will branch, rebase and merge as crazy, ending with a local git branch (eg "new-mforms") containing a lot of commits. You will make sure that your changes clearly applies to the most recent upstream version (git is really helpful here) and now you want to send your branch upstream.

Of course, you could prepare just a huge patch a commit it separately. You are discouraged to do so, though. There are some good reasons why your work should be re-applied commit-by-commit to CVS.

$ cd ~/public_html/moodlehead
$ git fetch
$ git checkout new-mforms
$ git cherry

This will show a list of commits on your local branch with the information whether they are or are not in the remote tracking branch, too. You are interested in commits with "+" prefix, ie. those that are added on your branch only. Use the following command to iterate through such commits and commit them one-by-one upstream:

$ git cherry origin/cvshead new-mforms | sed -n 's/^+ //p' | xargs -l1 git cvsupstream

Branching a plugin from CONTRIB

We do not have a git mirror of our CONTRIB area yet so you will have to create it yourself. Let us say you need to customize the favourite Certificate module for your client.

$ ssh nostromo
$ cd /pub/scm/git
$ mkdir mod-certificate

Create an executable bash script /pub/scm/git/cvsimport-mod-certificate with the following contents (modify as needed)

#!/bin/bash
CVSROOT=:pserver:anonymous@uk.cvs.moodle.org:/cvsroot/moodle
MODULE=contrib/plugins/mod/certificate
INSTALLDIR=mod-certificate
LOGFILE=mod-certificate.log
git cvsimport -p x -v -k -o cvshead -d $CVSROOT -C $INSTALLDIR $MODULE &> $LOGFILE

Run this script at nostromo for the first time to fetch the whole history of the Certificate module. Then you can run it regularly (every hour or so shall be enough) to keep your mirror up-to-date. Now let us create a working copy of this contrib module. At your localhost:

$ cd ~/public_html/moodle19/mod
$ git clone ssh+git://nostromo/pub/scm/git/mod-certificate certificate
$ cd certificate
$ git checkout -b MOODLE_19_STABLE origin/MOODLE_19_STABLE
In order to ignore the new directory in your working area, add the line
/mod/certificate
to either
.gitignore
or to
.git/info/exclude
(I prefer the later)
$ cd ~/public_html/moodle19
$ echo /mod/certificate >> .git/info/exclude

Do not forget you have to manually include the certificate in all deployment processes as discussed above. As it is not part of your moodle19 checkout, it will not be pushed neither archived etc. If I understand it correctly, git submodules feature can be handy here but I haven't played with it yet.

Appendix

Credits

A big thank you to Penny, Dan and Nigel for helping me with my first steps with git. Kudos for Martín and others from Catalyst for their contribution to the git-cvs integration tools.

See also