Working with GIT repository

Git is a free & open source, distributed version control system designed to handle everything from small to very large projects with speed and efficiency.

Every Git clone is a full-fledged repository with complete history and full revision tracking capabilities, not dependent on network access or a central server. Branching and merging are fast and easy to do.

In order to work with GIT you first have to understand and get used to work with multiple branches.

For a better understanding of the branch meaning and philosophy, one can be inspired from here: http://www-cs-students.stanford.edu/~blynn/gitmagic/ch04.html

This document examples are based on Douglas Hubler's repository on git-hub: http://github.com/dhubler/sipxecs

Working with GIT repository in local mode

A developer should be aware of three things in order to locally work with GIT repositories:

Download source code from the repository
Make your changes
Generate patches

There are two repositories involved: the remote repository (Douglas's on git-hub called origin repository) and your copy, called local repository

Download source code from the repository

Sources have to be downloaded in read-only mode on a chosen path on local computer, so there is no danger to overwrite the original code:

git clone git://github.com/dhubler/sipxecs.git

Example:

[mirceac@decebal ~]$ mkdir work
[mirceac@decebal ~]$ cd work
[mirceac@decebal work]$ git clone git://github.com/dhubler/sipxecs.git
Initialized empty Git repository in /home/mirceac/work/sipxecs/.git/remote:
Counting objects: 127119, done.remote:
Compressing objects: 100% (29946/29946), done.remote:
Total 127119 (delta 84094), reused 126491 (delta 83609)Receiving objects: 100% (127119/127119), 751.56 MiB | 1.69 MiB/s, done.
Resolving deltas: 100% (84094/84094), done.Checking out files: 100% (11021/11021), done.
[mirceac@decebal work]$ ls
sipxecs

Now, verify to what branch you are positioned using the following command:

git status

Use the following command to list all visible branches

git branch

The origin repository has many branches and you have to relay your work on one of them: master-4.2 Sometimes this branch is hidden and you have to make it visible

Use the following command to list all branches

git branch -a

Note: The branch: master is not the present locus of development – that 'branch' reflects the state of a tree that stayed in step with the former Avaya SVN tree. Almost certainly you wish to use: master-4.2 which is the real "master" as of November 2010

How to make branch master-4.2 visible and be positioned on it

git checkout -b master-4.2 origin/master-4.2

Watch the following code-snipped to accomplish this

Example:

[mirceac@decebal sipxecs]$ git branch
* master
[mirceac@decebal sipxecs]$ git branch -a
* master
  remotes/origin/HEAD -> origin/master
  remotes/origin/master
  remotes/origin/master-4.2
  remotes/origin/release-4.2
[mirceac@decebal sipxecs]$ git checkout -b master-4.2 origin/master-4.2
Branch master-4.2 set up to track remote branch master-4.2 from origin.
Switched to a new branch 'master-4.2'
[mirceac@decebal sipxecs]$ git status
# On branch master-4.2
nothing to commit (working directory clean)
[mirceac@decebal sipxecs]$ git branch
  master
* master-4.2
[mirceac@decebal sipxecs]$

Make your changes

Before starting working, you have to make sure that you are in sync with the latest source code. Assuming that you have to base your work on master-4.2 branch follow the steps from below:

ATTENTION: do not make any change or commit on master-4.2 branch. Always create a new branch for your changes

Run the commands from below:

git fetch origin //make sure that you are in sync with the remote repository (origin)
git checkout master-4.2 //move to master-4.2 branch, because we want to base our work on this
git rebase origin/master-4.2 //rebase your master-4.2 branch with the origin master-4.2 branch just to keep in sync with the latest source code
git checkout -b TEST //create an position to a new branch called TEST, the branch were your changes will be performed

TIP: if there is a branch you don't like you can always delete it using:

git branch -D TEST

...after all your changes are done and you are prepared for the final step: generate patch, run the following commands

git status //to verify what files are new and what are changed
git add <file_path> //if there are newly created files on your branch
git commit -a //commit your work

use git commit -a --amend if you want that your changes to be on top on a previous commit - in this way all will be included in a single patch

NOTE: for every commit will be generated one single patch (unless git commit -a --amend was used)

When git commit -a is used a vi editor is opened. Please the comments about the patch there and use :wq to actually write the changes (perform the commit)

git commt -a --amend will preserve previous commit comments and changes

TEST: Test Title

Description
# Please enter the commit message for your changes. Lines starting# with '#' will be ignored, and an empty message aborts the commit.
# Committer: Mircea Carasel
# On branch TEST
# Changes to be committed:
#   (use "git reset HEAD ..." to unstage)
#       modified:   sipXconfig/neoconf/etc/freeswitch/freeswitch.xml
#~

As a rule, after the title a blank line should be inserted and then the patch description

Example:

[mirceac@decebal sipxecs]$ git checkout master-4.2
Switched to branch 'master-4.2'
[mirceac@decebal sipxecs]$ git status
# On branch master-4.2nothing to commit
(working directory clean)
[mirceac@decebal sipxecs]$ git rebase origin/master-4.2
Current branch master-4.2 is up to date.
[mirceac@decebal sipxecs]$ git status
# On branch master-4.2
nothing to commit (working directory clean)
[mirceac@decebal sipxecs]$ git checkout -b TEST
Switched to a new branch 'TEST'
[mirceac@decebal sipxecs]$ git status
# On branch TEST
nothing to commit (working directory clean)
[mirceac@decebal sipxecs]$

****after all your changes are done****

[mirceac@decebal sipxecs]$ git status
# On branch TEST
# Changed but not updated:
#   (use "git add <file>..." to update what will be committed)
#   (use "git checkout -- <file>..." to discard changes in working directory)
#
#    modified:   sipXconfig/neoconf/etc/freeswitch/freeswitch.xml
#
no changes added to commit (use "git add" and/or "git commit -a")
[mirceac@decebal sipxecs]$ git commit -a
[TEST 747365d] UC-TEST: Patch title
 1 files changed, 1 insertions(+), 1 deletions(-)
[mirceac@decebal sipxecs]$ git status
# On branch TEST
nothing to commit (working directory clean)

Generate patches

In order to correctly generate a patch you have to make sure that your branch is rebased with the origin's master-4.2 branch, because while you performed your changes it is very likey

that some other developers performed other changes that are commited on the remote branch (origin)

Run the commands from below:

git fetch origin //make sure that you are in sync with the remote repository (origin)
git checkout master-4.2 //move to master-4.2 branch, because we want to base our work on this
git rebase origin/master-4.2 //rebase your master-4.2 branch with the origin master-4.2 branch just to keep in sync with the latest source code
git checkout TEST //move to your branch
git rebase master-4.2 //keep in sync your branch with your master-4.2 branch that now is in sync with origin's master-4.2

If rebase cannot be performed automatically, git may require you to manually perform some changes.

Example:

Falling back to patching base and 3-way merge...
Auto-merging sipXconfig/neoconf/src/org/sipfoundry/sipxconfig/bulk/csv/Index.java
CONFLICT (content): Merge conflict in sipXconfig/neoconf/src/org/sipfoundry/sipxconfig/bulk/csv/Index.java
Auto-merging sipXconfig/neoconf/src/org/sipfoundry/sipxconfig/common/AbstractUser.java
Auto-merging sipXconfig/neoconf/test/org/sipfoundry/sipxconfig/bulk/ldap/UserMapperTest.java
CONFLICT (add/add): Merge conflict in sipXconfig/neoconf/test/org/sipfoundry/sipxconfig/bulk/ldap/UserMapperTest.java
Auto-merging sipXconfig/web/src/org/sipfoundry/sipxconfig/site/admin/ldap/LdapServer.java
Failed to merge in the changes.Patch failed at 0001 XX-6279: Import contact information from LDAP
When you have resolved this problem run "git rebase --continue".If you would prefer to skip this patch, instead run "git rebase --skip".
To restore the original branch and stop rebasing run "git rebase --abort".
[mirceac@decebal sipxecs]$ git add sipXconfig/neoconf/src/org/sipfoundry/sipxconfig/bulk/csv/Index.java
[mirceac@decebal sipxecs]$ git add sipXconfig/neoconf/test/org/sipfoundry/sipxconfig/bulk/ldap/UserMapperTest.java
[mirceac@decebal sipxecs]$ git rebase --continue

git format-patch master-4.2 -o <output directory>

[mirceac@decebal sipxecs]$ git format-patch master-4.2 -o /home/mirceac/patches/
/home/mirceac/patches/0001-UC-TEST-Patch-title.patch
[mirceac@decebal sipxecs]$

git checkout sipXconfig/neoconf/etc/freeswitch/freeswitch.xml

Working with GIT repository in remote mode

The work in remote mode introduces a new term: upstream

Basically we will have:

upstream repository is git-hub Douglas's repository
origin your git-hub repository after forking
local is your local copy of your origin repository

Essentially, there are not big differences but you have to be aware that you are working now with three repositories. What is nice working in remote mode is that all your work will be stored on git-hub, you can create your own branches to keep any experimental/prototyping work you may want and in the same time to share it with everyone on git-hub

In order to set-up such environment follow below steps

Create an account on git-hub and add open-source repository (free)
From git-hub project page, fork Douglas's project into your own repository
Create ssh keys on both sides: local and on your git account(to prepare your local clone): http://www.question-defense.com/2009/02/04/add-a-ssh-key-to-your-github-account-for-a-linux-server
Clone your project in read/write mode
NOTE: Use: ssh-add ~/.ssh/id_rsa if you cannot get sources in read-write mode after adding ssh key
Commands:

  git clone git@github.com:mirceac/sipxecs.git
  //At this point you have tracked only your repository (origin)
  git remote (or git remote -v)
  return: origin

Track upstream remote repository (Douglas's):

   git remote add upstream git://github.com/dhubler/sipxecs.git (note the read-only url, there is no chance to write on upstream)
   git remote
   return: origin
           upstream

In order to keep in sync the upstream repository and origin repository (yours)

git checkout master-4.2 //move to master-4.2 branch
git fetch upstream //get latest code from upstream
git rebase upstream/master-4.2 //rebase your local master-4.2 branch repository with upstream
git status //to verify if your local branch has something that needs to be pushed to origin
git push origin +: //push on origin

NOTE: In order to automatically update a specific branch (master-4.2),
instead of git fetch upstream it is recommended to use:
git pull upstream master-4.2
This command will automatically align your master-4.2 branch with the upstream master-4.2 performing automatic rebase

NOTE: +: means that during rebase you may need to do some manual merging and your local git history may become different than origin git history and you need force push

Assuming that you developed on branch TEST, follow below steps to push them on origin

Perform any commit/rebase operation as explained above
Merge changes on your local master-4.2 repository
Push your master-4.2 repo on origin

Commands:

git checkout master-4.2  //move to master-4.2 branch
git rebase TEST //push TEST changes on top of your master-4.2 branch
git push origin +: //push your local master-4.2 branch on origin

Send your changes upstream: From your project's page, click the "pull request" button

The upstream owner may accept or may reject your commit

Some documentation links:

http://git-scm.com/

http://help.github.com/forking/
http://stackoverflow.com/questions/67699/how-do-i-clone-all-remote-branches-with-git
http://www.question-defense.com/2009/02/04/add-a-ssh-key-to-your-github-account-for-a-linux-server
http://www.kernel.org/pub/software/scm/git/docs/git-merge.html