GIT Part 2 - Installation and Set Up

GIT Part 2 - The technical parts

In my previous post I talked about the setup I had chosen with regards to GIT. In this post I talk about actually putting it into action. 

Installing GIT on Centos

Below are the steps I took to install git on Centos: I chose to do the installation from the graphical interface. I normally use the terminal but I was writing a guide for my colleagues for when/if they had to follow my installation steps, I took this blog from there. So, to add GIT onto the box:

·         Find 'Add/remove Software' from the menus.

·         Search for ‘Git’ and download the latest versions of:

o   Git (core and tools)

o   Git Daemon

o   Git Gui

o   Git web (if you want it)

·         It may require some dependencies.

·         Once installed the GIT repositories are under

o   var/lib/git

Or, yum install git if you have the dependencies and repositories added and want to do it from the terminal. 

Live: A copy of http://joemaller.com/990/a-web-focused-git-workflow/

So on Live we want to create a git repo that sits over the live code which is our PRIME. The live code is in /var/www/html.

$ cd /var/www/html

$ git init

$ git add .

$ git commit -m"initial import of pre-existing web files"

This creates an initial repository over /var/www/html and adds all of the files in it to the staging area:

Explanation Note: There are the files in the folder, the files that have been staged/in the index, and the files that are in the repo.

• The files that are in the index are those that are in the repo, plus those from the folder that have been staged. 
• Staging is telling the repo what files want to be put into the repo in the next commit.
• Committing is adding the files into the repo.

Once the files are in the index (staging area), it is all committed with a message.

Next we want to create HUB.

$ cd /; 

$ mkdir git; (or whatever you want to call it, e.g. hub.git)

$ cd git

$ git --bare init

This creates a bare repo in HUB (A repo with no code checked out or a repo with no code viewable when browsing to the folder)

Now, from inside PRIME, we want to add HUB as a remote repository so we can then push the master from PRIME to HUB

$ cd var/www/html

$ git remote add hub /git (or whatever you called it from above)

$ git remote show hub 

   (will show your hub)

$ git push hub master

The Hooks

Hooks are rules/scripts that can be set to automatically run when something happens in a GIT repository. We want to make sure that the two repositories are kept in sync.

The HUB hook - Post Update

In the .git folder (the hidden folder) within /git (or whatever you called it), there is a hooks folder. There are lots of sample hooks in there, we want to rename 'post-update.sample' to 'post-update' and then make sure its contents are:

#!/bin/sh

echo

echo “*** Pulling changes into Prime [Hub’s post-update hook]”

echo

cd $/var/www/html || exit

unset GIT_DIR

git pull hub master

exec git-update-server- 

The script swaps to PRIME and then does a pull from HUB into PRIME with the master branch. This will then update the code in the working directory.

The PRIME hook - Post Commit. 

Imagine that someone accidentally changes code in PRIME (ftp or direct access). The code for the website will change, but the git repos will be out of date. Assuming that the code change is checked in then at least the PRIME repo is up to date. But what about HUB and therefore (because this is the one we connect to), DEV?

In /var/www/html there will be a hidden folder called .git which will have the hooks folder in it. In this folder there probably isn’t one of the files that we need -> 'post-commit', so create it. (I just copied one of the other files and renamed it). The file should have the content of:

#!/bin/sh 

echo 

echo "**** pushing changes to Hub [Prime's post-commit hook]" 

echo 

git push hub

This script will simply push the contents of the repo to HUB. (This will, in turn, make PRIME pull HUB again, but oh well).

Testing

I tested this by changing a file in PRIME. (I changed the background colour of a part of a test page on moodle and transferred the file up to PRIME).

In the terminal I ran:

cd $/var/www/html

git status

git add [file name]

git commit -m”Test Commit”

This then outputted the output from the two hook scripts. 

The ignore file

As with many systems there are certain files that we don’t want to track and have in the repository. For Moodle there is at least: config.php. We also had a few others including gmail folders (blocks/gdata, blocks/gmail, auth/gsaml). Dev has its own config file (different addresses) and we didn’t want the accidental sending of emails.

The ignore file is a file that will ignore all of the files specified from being tracked if they are changed or from being added to the GIT repo.

In the .git folder add a .gitignore file and, on each line, put the files and folders that you want to ignore. Ours is: (I added this file in both PRIME and HUB.)

config.php

.htaccess

/blocks/gdata

/blocks/gmail

/auth/gsaml

We still have a slight issue though. We committed and pushed the above files to the repos and we need to get rid of them. To do this we need to run:

git rm --cached config.php

git rm --cached .htaccess

Commit and add a message.

This will remove the files specified from the git repo itself. 

Permissions

When I was testing all of this I was struggling to get the correct remote repo commands to work when connecting from my DEV machine. In the end I found it to be permissions.

I created a user and group called 'git' and gave them the correct writes over the git repos:

chgrp –R git [location of HUB]

chmod –R g+swX [location of HUB]

chgrp –R git [location of PRIME]

chmod –R g+swX [location of HUB]

Now we should have a working live system.

Installing GIT on Centos (DEV)

A ‘git’ user must exist and be in the ‘git’ group. I removed any moodle files that I already had making sure that I kept the dev server specific moodle config.php file. I made sure GIT was installed following the same initial install steps from above. In a terminal window I then ran:

cd /var/www

git clone ssh://git@[ipadress]:[port]/[folder] html

This changes to the www folder and then attempts to clone the [folder] of our HUB from the ipaddress of the live server and create a git repo in html. It will also check master branch out. It will probably ask for a git password.

Note: I am happy to leave authentication between live and dev to always ask for the password and not store it in any keys. For windows to DEV I did keys.

I added the exact same ignore file to DEV as LIVE and copied in the config.php file from before.

Next I created some new branches on DEV:

cd/var/www/html

git branch newFeatures

git branch branchNameWhatever

Now I had a working copy of DEV.

Installing GIT on Windows

The following is an amalgamation of:

·         http://nathanj.github.com/gitguide/tour.html

·         http://help.github.com/win-set-up-git/

·         http://creatingcode.com/2010/02/getting-started-with-git-and-tortoisegit-on-windows/

I use GIT gui, tortoisegit and putty configuration for my setup.

• Download and install PUTTY (http://www.putty.org/) PUTTY will allow you to have a linux command line inside the windows terminal. But will also act as the SSH connection between the Linux GIT server and the desktop GIT. 
• I put all three of my PUTTY downloads into my in c:\tools\bin (which is also in the PATH of the computer (right click on computer, properties, advanced system settings, environmental variables and then edit the PATH. A semi colon is used to separate the paths))
• Download Pageant.  (http://www.chiark.greenend.org.uk/~sgtatham/putty/download.html) This will be used later to store the pubic/private keys for GIT so that every time you do a push/pull command over SSH you don’t need to put in the public or private key for each file
• Download Plink. (http://www.chiark.greenend.org.uk/~sgtatham/putty/download.html) This will be used later as an interface to the PUTTY back end.
• Download PuttyGen. (http://www.chiark.greenend.org.uk/~sgtatham/putty/download.html) This will create the public and private keys we will need later.
• Download and install GIT for windows. Called msysgit (http://code.google.com/p/msysgit/downloads/list). Download the .exe, run it and it will download and install GIT for windows. I kept everything default except the following options

a.       Default  location is fine to install to

b.      ‘Select Components’ -> Default is ok, except, make sure that ‘Windows Explorer Integration’ is ticked and all its options.

c.       ‘Adjusting your PATH environment’ ->  Run Git from the Windows Command Prompt

d.      ‘Choosing the SSH executable’-> Use (Tortoise) Plink. Now search for the plink.exe (I put all three of my downloads into my in

e.      ‘Configuring the line ending conversions’-> Checkout as-is, commit as Unix Style

• Download and install TortoiseGIT (http://code.google.com/p/tortoisegit/downloads/detail?name=TortoiseGit-1.7.6.0-32bit.msi&can=2&q=) this is a client gui based system to allow you to work with GIT easier.

a.       ‘Choose SSH Client’ -> TortoisePlink

b.      ‘Location’-> Default location is ok

Ok, so now we have GIT installed on Windows we need to link it to DEV and clone.

Step 1

Login to DEV and create a new user and new password (for each developer) and put this user in the ‘git’ group. Create a ssh folder and an ‘authorized_keys’ file:

Create a .ssh folder in the home folder

      e.g. /home/username/.ssh

Create an ‘authorized_keys’ file in this folder

      e.g. /home/username/.ssh/authorized_keys

The American spelling is required and there is no file extension.

Step 2

Now we need to add the private and public keys so we can communicate with the remote repo.

Run the puttygen.exe program that was downloaded earlier.

Click on ‘generate’

Wait for it to generate the private key and move your mouse around over the bar

Click save private key (I saved without a pass phrase and as private.ppk)

Click save public key (I saved as public.ppk)

Now we need to add the private key to pageant on our machine:

Run pageant

Double click on the pageant icon in the tray

Add the private key

Now we add the public key to the DEV server:

In your authorized_keys file paste your public key. (I copied it to a text file and FTP’s this up to the server so I could access it, alternatively use putty to ssh in.)

Step 3

I next had to make sure that the ssh folder and file had the correct permissions. So I ran:

$ chmod 700 ~/.ssh

$ chmod 600 ~/.ssh/authorized_keys

Step 4

Now we can clone the remote repo.

Get rid of any Moodle installations from the windows box (remember to save the config.php file)

In the folder level above your original ‘Moodle’ folder (for me it was xampp/httpd/moodle) right click on the folder and select ‘Git Bash Here’. (I clicked on httpd folder inside my xampp folder)

Once the command comes up type:

git clone ssh://[yourUsernameHere]@[ipaddressDEV]:22/git moodle

Assuming your public and private keys are set up correctly then you will get a clone of everything that is in git. It will add this to a new folder called Moodle and it will ‘checkout’ all of the current working branch.

Step 5

The next step is to add your configuration details.

Edit -> options

Then put in your username and your email address in both halves. (The left is this repo, the right is all repos.)

Step 6

We now need to configure our local copy of the branches so we can use them on our local machines. This includes:

·         Swapping the config file out

·         Deleting the htaccess file

·         ‘Ignoring’ these files on all future commits.

If the config file and .htaccess from ‘dev’ has come down then remove them both and put back the config file from your original moodle (or create one).

Assuming that tortoise git is installed. Right click on the following files and add to the ignore list:

·         config.php

·         .gitignore (will be created as you ignore the file above)

If the file is already in the repo then we need to delete it. Run the git bash (over the moodle folder) and type the following commands:

·         Git rm --chached config.php

·         Git rm --chached .htaccess

This should remove them from the commit and will also not have them show up when comparing the local copy to your last snapshot.

Removing Web Access to the GIT repository
To remove web access from GIT (as its at the root of the accesible website) we need to modify the .htaccess file on LIVE in PRIME. Add:

# deny access to the top-level git repository:
RewriteEngine On
RewriteRule \.git - [F,L]

Done

That should now be all set up and in the next post I talk about how we use our git setup. This includes branching, merging and checking in.