GIT Introduction

Git is a distributed source control system, that is lighting fast and different from client-server systems. In this tutorial, we will learn how to get started with Git. By the end of this tutorial, you should be able to create a Git repository, record snapshots of your project for safekeeping, and view your project’s history.

Setup

Download git from the following locations:

Create a new repository

create a new directory, and perform the following operation to create a new git repository.

git init

Executing git init creates a .git subdirectory in the project root, which contains all of the necessary metadata for the repo. Aside from the .git directory, an existing project remains unaltered (unlike SVN, Git doesn’t require a .git folder in every subdirectory).

Checkout a repository

create a working copy of a local repository by running the following command:

git clone /path/to/repository

when using a remote server, your command will be

git clone username@host:/path/to/repository

Workflow

Your local repository consists of 3 “trees” maintained by git:

  • Working Directory which holds the actual files
  • Index/Staging which acts as a staging area
  • HEAD which points to the last commit you’ve made.

Add & Commit

You can propose changes (add it to the Index) using:

git add <filename>

This is the first step in the basic git workflow. To actually commit these changes use

git add *

Now the file is committed to the HEAD, but not in your remote repository yet.

git commit -m "Commit message"

Pushing changes

Your changes are now in the HEAD of your local working copy. To send those changes to your remote repository, execute

git push origin master

Change master to whatever branch you want to push your changes to.

If you have not cloned an existing repository and want to connect your repository to a remote server, you need to add it with

git remote add origin <server>

Now you are able to push your changes to the selected remote server

Branching

Branches are used to develop features isolated from each other. The master branch is the “default” branch when you create a repository. Use other branches for development and merge them back to the master branch upon completion.

create a new branch named “feature_x” and switch to it using

git checkout -b feature_x

switch back to master

git checkout master

and delete the branch again

git branch -d feature_x

a branch is not available to others unless you push the branch to your remote repository

git push origin <branch>

Update & merge

to update your local repository to the newest commit, execute

git pull

in your working directory to fetch and merge remote changes.
to merge another branch into your active branch (e.g. master), use

git merge <branch>

In both cases git tries to auto-merge changes. Unfortunately, this is not always possible and results in conflicts. You are responsible to merge those conflicts manually by editing the files shown by git. After changing, you need to mark them as merged with

git add <filename>

before merging changes, you can also preview them by using

git diff <source_branch> <target_branch>

Tagging

It’s recommended to create tags for software releases. this is a known concept, which also exists in SVN. You can create a new tag named 1.0.0 by executing

git tag 1.0.0 3a5e1d87af

The 3a5e1d87af stands for the first 10 characters of the commit id you want to reference with your tag. You can get the commit id by looking at the log.

Logging

You can study repository history using:

git log

You can add a lot of parameters to make the log look like what you want. To see only the commits of a certain author:

git log --author=sean

To see a very compressed log where each commit is one line:

git log --pretty=oneline

Or mabe you want to see an ASCII art tree of all the branches, decorated with the names of tags and branches:

git log --graph --oneline --decorate --all

See only which files have changed:

git log --name-status

These are just a few of the possible parameters you can use. For more, see

git log --help

Replace local changes

In case you did something wrong, you can replace local changes using the command

git checkout -- <filename>

this replaces the changes in your working tree with the last content in HEAD. Changes already added to the index, as well as new files, will be kept.

If you instead want to drop all your local changes and commits, fetch the latest history from the server and point your local master branch at it like this

git fetch origin
git reset --hard origin/master

Useful commands

Here are few more useful git commands:

Built-in git GUI

gitk

Use colorful git output

git config color.ui true

Show log on just one line per commit

git config format.pretty oneline

Use interactive adding

git add -i

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