Git: Introduction to Branching

In real time, environment, there are minimum 3 branches.

a.   master: Where developers can actively contribute

b.   test: Before releasing the product to customer, code from master is cloned to test branch, and testing done here.

c.    production: Customer released code placed here.

Why to maintain branches?

it is required for developers to continue their work without messing other branches.

For example, there are 4 developers in a team and each developer is working on different features. If everyone keeps on committing their changes to master branch, it leads to so many conflicts. To resolve this, each developer can create their own local branch from master and contribute to their local branch. Once feature implemented, developer can do basic testing and merge the changes with master branch.

How to create a branch from master branch?

First make sure you are in 'master' branch, then execute below command to create new branch from master branch.

git checkout -b new_branch

How to merge new_branch changes to master branch?

Make sure you are in master branch and execute below command to merge the changes from new_branch to master branch.

git merge new_branch

Let’s visualize the same using below user interface.

http://git-school.github.io/visualizing-git/

When you launch above uri in browser, you can see below screen.

Let’s perform two commits by executing below command twice.

git commit

As you see above image, after performing first commit, master and HEAD are pointing to new snapshot.

Let me commit one more time.

Let me create and checkout new_branch from master branch by executing below command.

git checkout -b new_branch

As you see above diagram ‘new_branch’ is created and checkedout (HEAD is below new_branch).

Execute ‘git commit’ statement.

Since we are in new_branch, when you execute ‘git commit’ statement, it creates new snap shot for new_branch.

Let’s commit one more time.

Let’s checkout master branch by executing below command.

git checkout master

As you see the above diagram, HEAD is pointing to master branch.

Let’s execute ‘git commit’ thrice.

Merge the data from new_branch to master

If you want merge the data from new_branch to master branch, first you should be in master (checkout master) branch and execute 'git merge new_branch' command.

Let’s see the example practically

Step 1: Clone a git branch.

Syntax

git clone {repository_url}

$git clone https://github.com/harikrishna553/gitHelloWorld.git
Cloning into 'gitHelloWorld'...
remote: Enumerating objects: 26, done.
remote: Counting objects: 100% (26/26), done.
remote: Compressing objects: 100% (18/18), done.
remote: Total 26 (delta 3), reused 16 (delta 2), pack-reused 0
Unpacking objects: 100% (26/26), done.

My git repository looks like below.

$tree
.
└── gitHelloWorld
    ├── README.md
    ├── tempFile1.txt
    ├── tempFile4_copy.txt
    └── welcome.txt

1 directory, 4 files

Step 2: Add new file ‘master_file.txt’ to the branch.

$cd gitHelloWorld/
$
$touch master_file.txt

Step 3: Commit the changes.

$git status
On branch master
Your branch is up to date with 'origin/master'.

Untracked files:
  (use "git add <file>..." to include in what will be committed)

 master_file.txt

nothing added to commit but untracked files present (use "git add" to track)
$
$git add master_file.txt 
$
$git commit -m "Adding master file"
[master e05ed60] Adding master file
 1 file changed, 0 insertions(+), 0 deletions(-)
 create mode 100644 master_file.txt
$
$git status
On branch master
Your branch is ahead of 'origin/master' by 1 commit.
  (use "git push" to publish your local commits)

nothing to commit, working tree clean

Step 4: Create 'new_branch' from master branch

$git checkout -b new_branch
Switched to a new branch 'new_branch'
$
$git branch
  master
* new_branch

Step 5: Add new file ‘new_branch_files.txt’ and commit it to new_branch.

$touch new_branch_file.txt
$
$git status
On branch new_branch
Untracked files:
  (use "git add <file>..." to include in what will be committed)

 new_branch_file.txt

nothing added to commit but untracked files present (use "git add" to track)
$
$git add new_branch_file.txt 
$
$git commit -m "Adding a text file to new_branch"
[new_branch 2255b77] Adding a text file to new_branch
 1 file changed, 0 insertions(+), 0 deletions(-)
 create mode 100644 new_branch_file.txt

Step 6: Merge new_branch to master branch.

Check out master branch

git checkout master

Merge new_branch with master branch

git merge new_branch

$git checkout master
Switched to branch 'master'
Your branch is ahead of 'origin/master' by 1 commit.
  (use "git push" to publish your local commits)
$
$tree
.
├── README.md
├── master_file.txt
├── tempFile1.txt
├── tempFile4_copy.txt
└── welcome.txt

0 directories, 5 files

$git merge new_branch
Updating e05ed60..2255b77
Fast-forward
 new_branch_file.txt | 0
 1 file changed, 0 insertions(+), 0 deletions(-)
 create mode 100644 new_branch_file.txt
$
$tree
.
├── README.md
├── master_file.txt
├── new_branch_file.txt
├── tempFile1.txt
├── tempFile4_copy.txt
└── welcome.txt

0 directories, 6 files
$
$git status
On branch master
Your branch is ahead of 'origin/master' by 2 commits.
  (use "git push" to publish your local commits)

nothing to commit, working tree clean

As you see the output ‘new_branch_file.txt’ is copied to master branch.

Reference

http://git-school.github.io/visualizing-git/

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