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Why is Git Around?
 Consider we are working on some project, there are fi, f2, f3 files in one folder and
we want them to save them after changes. This will fill our hard disk if we want to
keep each version of file.
Project.zip Projectfinal.zip Projectfinal1.zip Projectfinal2.zip

Version Control System(VCS)
 a way to manage files and directories.
 track changes over time.
 recall previous versions.
 source control is subset of VCS.
 sharing on multiple computers

Centralized VCS
 Subversion (SVN)
• checkout
• update
• commit

Distributed VCS
 GIT
 Mercurial

GIT
 Created by Linus Torvalds, creator of Linux, in 2005
– Came out of Linux development community
– Designed to do version control on Linux kernel
 Goals of Git:
- Speed
- Support for non-linear development (thousands of parallel branches)
- Fully distributed
- Able to handle large projects efficiently

Features of GIT
 Snapshots, NOT differences
 Nearly every operation is local.
 Git has Integrity(checksum)
Storing data as snapshots of the project over time

Let’s Start with GIT
• Enter these lines (with appropriate changes):
git config --global user.name "John Smith“
git config --global user.email jsmith@seas.upenn.edu

The Three stage
architecture
 You modify files in your working
tree.
 You selectively stage just those
changes you want to be part of
your next commit, which
adds only those changes to the
staging area.
 You do a commit, which takes the
files as they are in the staging area
and stores that snapshot
permanently to your Git directory

Create and fill a repository
cd to the project directory you want to use
• This creates the repository (a directory named .git)
• You seldom (if ever) need to look inside this directory
Type in git init
• Period means “this directory”
• This adds all your current files to the repository
Type in git add .
• You can use a different commit message, if you like
Type in git commit –m "Initial commit"

Clone a repository from elsewhere
 git clone URL
 git clone
https://github.com/ishant
k/DSA2020-1
 Instead of getting just a
working copy, Git receives a
full copy of nearly all data that
the server has.

Lifecycle of status of files
Lifecycle of status of your files.

Working with your
own repository
 A head is a reference to a commit
object
 The “current head” is called HEAD
(all caps)
 This results in a linear graph:
A  B  C  … HEAD

Back tracking, Removing, Rename
 Rolling back to last commit
$ git checkout HEAD [filename]
$ git diff
 Skipping staging area
$ git commit –a –m “your message”
 Remove File from Staging
$ git reset HEAD [filename]
 Remove file in Git
$ git rm [filename]
 Rename file in Git
$ git mv [current_filename] [changed_filename]

Initial commit
Second commit
Third commit
Bob gets a copy
Fourth commit
Merge
Bob’s commit
Multiple versions

Branching
 View branch
 Make new branch
 Merge branch
 Delete Branch

GITHUB
 GitHub.com is a site for online storage of Git repositories.
– You can create a remote repo there and push code to it.
– Many open source projects use it, such as the Linux kernel.
– You can get free space for open source projects, or you can pay for private projects.
 Question: Do I always have to use GitHub to use Git?
 Answer: No! You can use Git locally for your own purposes. – Or you or someone
else could set up a server to share files. – Or you could share a repo with users on
the same file system, as long everyone has the needed file permissions).

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Git training (basic)

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