A brief Git introduction

git-intro.md

Why Git:

• Local and distributed :
  • So what?
  • Local is faster : Think about it, reading from HDD/RAM is faster than reading from www.imslow.com each time.
  • It not only saves your time on local operations like read history, diff, work offline [-who doesn’t have internet??] but also makes collaborating tools like Jenkins faster to act.
• Branch policies & Code review (GitHub, GitLap, VSTS ets): Tools made upon git have eligant feature like
  • Code review: Following pull request workflow (more on this later), you can set branch policies to make sure that a code is reviewed before getting into the branch.
  • Branch policies to prevent anyone directly committing into the branch like prod branch 'master' (similar to trunk)
• Lightweight:
  • Git's repositories are much smaller than Subversions (for the Mozilla project, 30x smaller). ref: https://git.wiki.kernel.org/index.php/GitSvnComparison

Git Basics - I : Local and remote repository

• Because git is lightweight, when you clone a project (like svn checkout), it copies the whole repository i. e all the branches (on just one like svn), all commit history etc]
• Remote repository is generally referred with prefix origin/ and local with no prefix. Let's say in reliant you have these 5 branches master (the prod branch like svn trunk), autopay, nest, prepay and one-click then if you are working in git you may probably have remote repo as {origin/master, origin/autopay, origin/nest, origin/prepay, origin/one-click} and local repo as {master, autopay, nest, prepay, one-click}
• Hence a important point for fellows coming from SVN : **> git commit ** is commit operation to local repository and makes changes appear in remote repo you will have to do ** > git push *** but more on that later

A Typical day in dev's life

• Code :

Calcu.java

public void greet(String name) {
    system.out.println("Hello "+name);
}

• New requirement came in: greet in spanish

Steps:

• Identify/determine the url of repository say : http://vsts.com/greet-app
• Checkout project : git clone http://vsts.com/greet-app
• Remember as said you have all the branches in local repo. By default you are on master branch
• create a new local branch for it -- espanol-greet

> git checkout -b espanol-greet

• You may like to create a corresponding remote branch for it at some point of time; for ease of understanding let's do it now

git push -u orgin espanol

• Open file Calcu.java and edit

public void greet(String name, String lang) {

    if(lang != null && lang.equals("es")) {
        System.out.println("Ola "+name);
    } else {
        system.out.println("Hello "+name);
    }
}

• Add file to staging area > git add .
• Commit file to local repo ``` > git commit -m "Adding support for spanish"

Again, this commit is local to your repository and hence not visible to others.

• Push your work to remote repository i.e origin/espanol-greet > git push

• Create a Pull request to origin/develop i.e Merge your code to develop : You might have origin/develop branch, code from which is deploy to dev -> test ==promote==> stage --> test. To merge your code from orgin/espanol ===> origin/develop you will need to create pull request. It's a simpe operation of VSTS site of around 2 drop-down, 2 text box and 3 button clicks. More on that later.

• Once pull request is made, it must be reviewed and approved by reviewer to get it merged.

A typical git lifecycle: clone ====> FETCH (update your repo before committing ) ====> work/code ======> add modified files to staging area : git add . ====> commit (could be more than one) git commit -m <message> ====> git push (***could be more than one ***) ======> Pull request to origin/develop ====> approve & merge ====> test in dev/stg ====> pull request from origin/develop to origin/master ====> test in prelive ====> prod release

Simply : clone/fetch ===> add ===> commit ====> push ===> pull request

And that's a bird eye view of small set of git operations. More on it later