This document discusses version control and Git. It defines key terms like VCS, check-in, check-out and commit. It explains how version control allows versioning of files, manages changes from multiple users by storing files in a central repository. It describes how Git is different from other VCSs in that the repository is seen as a whole rather than individual files, branches are versions of the repository rather than copies, and the entire repository can be accessed locally. It also covers the basic Git commands and workflows for working with files, branches and remote repositories.

1. VERSION CONTROL
AND GIT
Sreedevi Vedula

2. Terms used
• VCS – Version Control System
• Check-in – Storing files in the VCS Central Repo
• Check-out – Getting files from the VCS Central Repo
• Commit – Git’s term for check-in

3. What does version control do?
• Version files
• Manage changes from multiple users
• Store the versions in a central repository

4. Version Files
Version 1
Version 2
Version 1

5. Multi-User Check-in
Subsequent
Check-in at
9 A.M
Checkout
at 8 A.M.
Checkout
at 10
A.M.
Check-in
at 11 A.M.
VCS: “I
am
good”

6. Multi-User Check-in
Concurrent - Different Files
Check-in
at 9 A.M.
Check-out
at 8 A.M.
Check-out
at 8 A.M.
VCS: “I
am
good”
Check-in
at 9 A.M.

7. Multi-User Check-in
Concurrent – Same Files
Check-in at
9 A.M.
Check-out
at 8 A.M.
Modified lines:
Line 5
Line 6
Holiday.py
Modified lines:
Line 10
Line 11
Holiday.py
Merge
Check-in
at 10 A.M.
Check-out
at 8:30 A.M.

8. Multi-User Check-in
Concurrent – Same Files
9 A.M.
Merge
Conflict
Line 5
Line 6
Holiday.py
Line 5
Line 6
Holiday.py
10 A.M.
Check-out
at 8 A.M.
Check-out
at 8 A.M.

9. Take Snapshots of Repos
Release 1.0 Release 2.0

10. Create branches
Release 1.0
E-Fixes
Version 12 Version 13
Version 1 Version 2

11. Merge branches
Release 1.0
E-Fixes
Version 12 Version 13 Version 14
Release 2.0

12. Git – How is it different
• Repository is seen as a whole and not as files
• Commit a repo and not files
• Go back to a specific version of a repo and not a file
• Repository is local and not remote
• Entire repository can be accessed locally
• No need to be connected to the remote server
• Branches are also versions of the repo and not copies of it
• Create a new branches in the same filesystem
• Pull branches from remote server into the same filesystem
• Work on two branches simultaneously in the same file system
• Forking user repo is inherent
• Github server provides you option to fork your copy of the repo which
helps collaboration initiated from the user side
• Free github account to host experimental projects

13. Git Repository
• git init
• Creates a git local repository
• .git directory
• A hidden directory in the repository which has the repo information
like version history of all the files, branch information
• git clone <url>
• Download the remote repository at <url> and create a local
repository for it

14. Git – Working with files
• The four states for a file
• Untracked – The files that are not never added to git are in this stage
• Unmodified – Files that are in the git repo, but not edited.
• Modified – Files edited by you after getting changes from the repo
• Staged –Files that are staged for commit
• git add
• Moves untracked files / modified files to staged state
• git rm
• Move staged files to modified / untracked files
• git diff
• Show changes made to files in modified state
• git diff –cached
• Show changes made to files in staged state
• git commit
• Save changes to the local repository
• git checkout – <file>
• discard changes in working directory
• git reset
• Reset or revert to an earlier commit
• git log
• Show the commit history of the

15. Git – Working with branches
• git checkout –b
• Create a new branch and switch to it
• git branch
• List all the branches
• git merge <branch>
• Merge the current branch with the changes from <branch>
• git rebase <branch>
• Modify the development history of the current branch by pulling the
commits from it since the common latest commit <A> of the two
branches, apply the commit history of <branch> since <A> to the
latest commit to the current branch and re-apply the pulled-out
commits on top of it.

16. Git – Connecting with remotes
• User configuration
• Repo Level - .git/config
• Global Level - ~/.gitconfig
• System Level - /etc/gitconfig
• Know your git configuration
• git config

17. Git – working with remotes
• The three transfer protocols that help upload / download content from the remote
repositories
• Git
• Fastest Transfer
• No authentication
• SSH
• Authenticated Write access
• Efficient data transfer
• Encrypted data transfer
• Http
• Easy to setup
• Can serve read-only repos
• Corporate firewalls usually allow HTTP traffic
• Slow data transfer
• git clone <url>
• Creates a local repository for a remote repo given by <url>
• git remote add <remote-name> <url>
• Add a git remote specified by <remote-name> for the repo at <url>
• git pull <remote-name> <branch>
• Pull changes from the branch <branch> of remote repo mapped to <remote-name>
• git push <remote-name> <branch>
• Push changes to the branch <branch> of remote repo mapped to <remote-name>

18. References
• http://git-scm.com/book