[rules-dev] Getting started with git on drools for svn guys

[Geoffrey De Smet]

      Purpose

This document shows you how to use Git, just as you were using SVN in 
the past. It is to get you guys up and running with git as soon as 
possibleby relying on your SVN knowledge and it is focuses on what you 
want to do in drools.
This document does not reallyteach you Git.Git is not just SVN++, it is 
much more and you should take some time to learn that too.


      Terminology

SVN trunk is renamed to Git master. A branch is still a branch. A tag is 
still a tag.
Translation note: trunk == master

The SVN central repository is now the referencerepository on github, see 
https://github.com:droolsjbpm/droolsjbpm 
<https://docs.google.com/document/d/1xfC_R61ASX12zfgmarR_3leTjG8paUmO9q5qNVtTMRg/edit?hl=en>.


    Part 1: Need to know


      Preparation

If:

    * you’ve done the preparation in the dev list mail
          o and the correction too, skip to section Getting the source
            code locally.
          o haven’t done the correction yet, do this first (and the skip
            to that section):

                + Step 4 stated:
                      # $ git config --global user.name myUsername  // WRONG
                + Correct that by running:
                      # $ git config --global user.name "My Name"
                      # $ git config --global -l
    * you haven’t done the preparation yet, do it now, as stated below.


Full preparation:

    * 1) Install git for your OS
          o 1a) Linux: Install the package git (and optionally gitk)
                + $ sudo apt-get install git
                + $ sudo apt-get install gitk
          o 1b) Windows: Use the icon on the right
            on<http://git-scm.com/>http://git-scm.com<http://git-scm.com/>
          o 1c) Mac OSX: Use the icon on the right onhttp://git-scm.com
            <http://git-scm.com/>
                + Optionally install gitx fromhttp://gitx.frim.nl/
    * 2) Install git in your IDE
          o 2b) Eclipse: Install the EGit plugin.
                + Menu Help, menu item Install new software.
                + Work with update site Helios, open Tree item
                  Collaboration, tree item Eclipse EGit.
          o 2c) IntelliJ: Enable the git plugin (if not enabled):
                + Menu file, menu item Other Settings, menu item
                  Configure plugins.
    * 3) Get a Github
      account:<https://github.com/signup/free>https://github.com/signup/free<https://github.com/signup/free>
    * 4 <https://github.com/signup/free>) Configure git correctly
      (Github also tells you this):
          o $ git --version
          o git version 1.7.1
          o $ git config --global user.name "My Full Name"
          o $ git config --global user.email myAccount at gmail.com
            <mailto:myAccount at gmail.com>
          o $ git config --global -l
          o user.name=Geoffrey De Smet
          o user.email=ge0ffrey.spam at ...
    * 6) Push your public key to github:
          o Follow the instructions
            onhttp://github.com/guides/providing-your-ssh-key


      Getting the source code locally

First move your old SVN working directory aside, so you’re not confused 
that you shouldn’t work there any more:
$ cd projects
$ mv drools drools-oldsvn

Now you’re ready to get the sources with git. In SVN this is a svn 
checkout, but in Git this is called a git clone. Prefer the faster, 
stabler git protocol over the slower https protocol:
$ git clone git at github.com:droolsjbpm/droolsjbpm.git droolsjbpm
Next go into that directory
$ cd droolsjbpm

So what’s the command git checkoutfor? To switch to another branch, but 
in the same working directory. In SVN you also use svn checkoutfor that.
Translation note: svn checkout == git clone (new repository) OR git 
checkout (change branch)

Follow the instructions in the README.txt to set up your Eclipse or 
IntelliJ again.


      Getting changes from others

So Mark and Edson changed something in drools-core in the reference 
repository. How do I get those changes? In SVN this is svn update, but 
in Git this is a git pull.
$ git pull
Translation note: svn update == git pull


      Making changes

While making your changes, do the same as in SVN: git add, git 
rm(instead of svn delete), git status.
Translation note: svn delete = git rm

After making your changes, you ‘ll want to do a git commit(when you’re 
done with a changeset) and a git push(to share those changes with the 
rest of the team). To recap: doing a git commitdoes not push your 
changes to the remote repository yet, you also need to do a git push.
$ git commit -m “JBRULES-123 fix testcase”
$ git push
Translation note: svn commit == git commit + git push


    Part 2: Tell me more


      Extra terminology

What is rebasing? A rebaseis an alternative manner of merging: instead 
of merging your changes with the incoming changes, it takes the incoming 
changes and applies your changes on top of that. For example:
$ git pull --rebase

What is origin? Because git can work with multiple remote repositories 
(usually forks of the same project), the default remote repository is 
known as origin. If you’ve cloned the reference repository, then 
originis the reference repository. If you’ve forked the reference 
repository as A and cloned A, then originis A.


      Branching

Usually we’ll have 2 types of branches: release branches and topic branches.
To switch to another branch, just use git checkout:
$ git checkout 5.1.x

To create a branch do:
$ git checkout -b 5.2.x


      Release branching

A release branches is copied from the master branch and only receives 
bug-fixes. It is separated from the master branch so no unstable 
features or improvements (pushed by other developers) leak in.
For example: $ git checkout 5.1.x

Cherry pickingis very interesting to pick bug-fixes from the master 
branch into the release branch.


      Topic branching

A topic branch is copied from the master branch and is eventually merged 
back into the master branch. Its changes are to disruptive to other team 
members to be committed to the master immediately.
For example: $ git checkout trueModify

Rebasingis very interesting when you’re working on an experimental 
feature in a topicbranch for the last few weeks and you want to have the 
latest changes of master(=trunk) in there too (= sync up with master):
// on my the myTopic branch
$ git rebase master

After your topic branch is stable, you’ll merge it into the master branch:
$ git checkout master
$ git merge trueModify


    Learn more

Do you want to reallylearn Git?
Read the Pro Git book (freely available online):http://progit.org/book/
You’ll easily gain the time you spend reading that book, because Git is 
more than SVN++.
Read that book, especially if you’re going to do branching and merging!
Other references: Hibernate git tricks 
<http://in.relation.to/Bloggers/HibernateMovesToGitGitTipsAndTricks>, 
SVN crash course <http://git-scm.com/course/svn.html>, Git for Gnome 
developers <http://live.gnome.org/Git/Developers>, ...

-- 
With kind regards,
Geoffrey De Smet

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