Presentation show displays essential features of the most popular Version Controls System Git.

1. Version control system

2. What is a Version Control System (VCS)
 a software utility that tracks and manages changes to a file system.
 kind of "database". lets you save changes and take a look over time.
 tracks the addition, deletion, and modification actions applied to files and
directories.
 offers collaborative utilities to share and integrate these file system changes to
other VCS users.

3. Primary benefits of a VCS
 A complete long-term change history of every file.
 Branching and merging.
 Traceability

4. Most popular version controls systems
Source : https://www.openhub.net/
VCS’s in Open Source Projects

5. Centralized vs Distributed

6. “Tools” to get started with Git
 Git itself. Download from official site https://git-scm.com/downloads
 Git Bash. Convenient Command Prompt (Terminal) for Windows to run Git
commands and Unix commands such as cat, touch etc.
 Git GUI Clients : GitHub Desktop, GitKraken, SmartGit, SourceTree, TortoiseGit.
 Even more GUI clients at https://git-scm.com/downloads/guis
 IDE integrated Git tools and plugins to work with Git. Most IDE’s have built in tools
or plugins to support Git.

7. Git basic commands
 git init – initializes current directory as Git repository
 git add - adds file(s) to “Staging Area”
 git commit – creates new commit/version.
 git status – shows the working tree (files & directories) status
 git log – list commits
 gitignore – prevent files and directories from being version controlled.

8. File states

9. gitignore – Ignoring files
 .gitignore file specifies files that Git should ignore
 gitignore – specifies untracked files to ignore
 only untracked files can be ignored
 Files already tracked by Git are not affected
 .gitignore uses globbing patterns to match against file names
 untrack a file example : git rm --cached "New Microsoft Excel Worksheet.xlsx“
 untrack all “dll” files : git rm --cached *.dll

10. gitignore – Ignoring files (Examples)
Pattern Explanation Example matches
**/logs logs directories anywhere
in the repository.
logs/debug.log
logs/monday/foo.bar
build/logs/debug.log
**/logs/debug.log All debug.log files which
are in logs directory
logs/debug.log
build/logs/debug.log
but not
logs/build/debug.log
*.log
!important.log
debug.log
trace.log
but not
important.log
logs/important.log
All log files but not
the files named
important.log

11. The staging area
 git add - adds files, folders to the staging area
 Examples : git add <file>, git add <directory>, git add hello.py, git add .
 git commit – commits/saves files only existing in the staging area
 The staging area stores information on what will go into your next commit

12. Commits
 Every commit has SHA1 hash that uniquely represents a commit

13. Branching out – Introduction 1
 If you make some changes and commit again, the next commit stores a pointer to the
commit that came immediately before it.
 A branch in Git is simply a lightweight movable pointer to one of these commits.
 The default branch name in Git is master. git init command creates it by default and
most people don’t bother to change it.

14. Branching out – Introduction 2
 Every time you commit, the current branch (initially master) pointer moves forward
automatically.

15. Branching out – Creating new branch
 When you create a new branch it creates a new pointer pointing to the latest
commit.
 to create a new branch called testing run this git branch command:
$ git branch testing
 This creates a new pointer to the same commit you’re currently on.

16. Branching out – HEAD
 How does Git know what branch you’re currently on?
 It keeps a special pointer called HEAD
 this is a pointer to the local branch you’re currently on

17. Branching out – Switching branches
 To switch to the existing branch testing branch run the following command:
$ git checkout testing
 This moves HEAD to point to the testing branch

18. Branching out - Advancing
 After checking out testing branch let’s do another commit
 HEAD branch moves forward when a commit is made
 testing branch has moved forward
 master branch still points to the commit it was on when switched branches

19. Branching out – Switching back
 Let’s switch back to the master branch:
$ git checkout master
 HEAD pointer is moved back to point to the master branch
 the files in your working directory are reverted back to the snapshot that master
points to

20. Branching out – Diverging
 After checking out master branch let’s do another commit
 HEAD branch moves forward when a commit is made
 master branch has moved forward

21. Branching out – Some commands
 $ git branch – list branches
 $ git branch develop – create new branch develop
 $ git checkout develop – switch to develop branch
 $ git checkout -b hotfix – create hotfix branch and switch to it
 $ git branch -d issue1 – delete local branch issue1
 $ git branch -m developer develop – rename developer branch into develop

22. Merging – Initial state

23. Merging – Fast forwarding
 Merging hotfix into master by running the following commands :
$ git checkout master
$ git merge hotfix

24. Merging – Delete merged branch
 delete the hotfix branch, we longer need it, the master branch points at the same place
$ git branch -d hotfix
 add new commit C5 in iss53 branch

25. Merging - Three-way merge
 Merging iss53 into master
$ git checkout master
$ git merge iss53
 Git does a simple three-way by using common ancestor (C2) and two snapshots
(C4 & C5)

26. Merge Conflicts
 If you changed the same part of the same file differently in the two branches you’re
merging, Git won’t be able to merge them cleanly.
 you’ll get a merge conflict that looks something like
$ git merge iss53
Auto-merging index.html
CONFLICT (content): Merge conflict in index.html
Automatic merge failed; fix conflicts and then commit the result.

27. Merge Conflicts - Status
 Anything that has merge conflicts and hasn’t been resolved is listed as unmerged.
 If you want to see which files are unmerged at any point after a merge conflict, you can run git status:
$ git status
On branch master
You have unmerged paths.
(fix conflicts and run "git commit")
Unmerged paths:
(use "git add <file>..." to mark resolution)
both modified: index.html
no changes added to commit (use "git add" and/or "git commit -a")

28. Merge Conflicts – Resolution markers
 Git adds standard conflict-resolution markers to the files that have conflicts
 you can open them manually and resolve those conflicts
 your file contains a section that looks something like this:
<<<<<<< HEAD:index.html
<div id="footer">contact : email.support@github.com</div>
=======
<div id="footer">
please contact us at support@github.com
</div>
>>>>>>> iss53:index.html

29. Merge Conflicts - Finalization
 Remove conflict-resolution markers
 choose one side or the other or merge the contents yourself
 to use a graphical tool to resolve these issues, you can run git mergetool
 run git status again to verify that all conflicts have been resolved
 type git commit to finalize the merge commit

30. References
 https://www.atlassian.com/git/tutorials/saving-changes
 https://www.atlassian.com/git/tutorials/saving-changes/gitignore
 https://www.atlassian.com/git/tutorials/comparing-workflows/gitflow-workflow
 https://www.atlassian.com/git/tutorials/why-git
 https://www.atlassian.com/git/tutorials/what-is-version-control
 https://www.tigraine.at/2016/10/22/git-isnt-magic
 https://git-scm.com/book/en/v2/Git-Basics-Recording-Changes-to-the-Repository
 https://git-scm.com/book/en/v2/Git-Branching-Branches-in-a-Nutshell
 https://git-scm.com/book/en/v2/Git-Branching-Basic-Branching-and-Merging