What is the version control system and why we use it? The difference betwen GIT and Subversion?

1. GIT
&
SUBVERSION
Anonymous

2. WORKING ALONE
▪ Had code that worked, made a bunch of changes and saved it, which
broke the code, and now you just want the working version back…
▪ Accidentally deleted a critical file, hundreds of lines of code gone…
▪ Somehow messed up the structure/contents of your code base, and
want to just “undo” the crazy action you just did
▪ Hard drive crash!!!! Everything’s gone, the day before deadline.

3. WORKING IN TEAMS
▪ Whose computer stores the "official" copy of the project?
▪ Will we be able to read/write each other's changes?
▪ Do we have the right file permissions?
▪ Lets just email changed files back and forth.
▪ What happens if we both try to edit the same file?
▪ Kareem just overwrote a file I worked on for 6 hours!
▪ What happens if we make a mistake and corrupt an important file?
▪ Is there a way to keep backups of our project files?
▪ How do I know what code each teammate is working on?

4. SO WHAT CAN I DO?

5. VERSION CONTROL SYSTEM
▪ version control system (often called a source code control system)
does these things:
▪ tracks incremental versions (or revisions) of files and, in some cases,
directories over time.
▪ allows you to explore the changes which resulted in each of those versions
▪ Allows “check in” and “check out” of files so you know which files someone
else is working on
▪ Displays differences between versions

6. HOW IS IT WORK?

7. VCS USES A REPOSITORY
▪ check in: adding a new file to the repository
▪ check out: downloading a file from the repo to edit it
▪ you don't edit files directly in the repo; you edit a local working copy
▪ once finished, the user checks in a new version of the file
▪ commit: checking in a new version of a file(s) that were checked out
▪ revert: undoing any changes to a file(s) that were checked out
▪ update: downloading the latest versions of all files that have been recently
committed by other users

8. MERGING AND CONFLICTS
▪ Merge: Two sets of changes applied at same time to same files
▪ happens when two users check out same file(s), both change it, and:
▪ both commit, or
▪ one changes it and commits; the other changes it and does an update
▪ Conflict: when the system is unable to reconcile merged changes
▪ resolve: user intervention to repair a conflict. Possible ways:
▪ combining the changes manually in some way
▪ selecting one change in favor of the other
▪ reverting both changes (less likely)

9. SUBVERSION SVN
▪ Centralized version control systems.
▪ based on the idea that there is a single “central” copy of your project
somewhere (probably on a server).
▪ programmers will “commit” their changes to this central copy.
▪ automatically update the contents of any files that were changed.
▪ Programmers no longer have to keep many copies of files on their hard
drives manually.

10. DISADVANTAGES OF SVN
▪ The repository is centrally stored on a server.
▪ You need to be online to access.
▪ Performance is slow.

11. CENTRALIZED AND DISTRIBUTED VCS

12. VERSION CONTROL SYSTEM
Version Control System VCS
Centralized VCS
Subversion
Distributed VCS
Git

13. ▪ Linus Torvalds, 2005
▪ Came out of Linux development community
▪ Initial goals:
 free and open .
 Speed
 Support for non-linear development (thousands of parallel branches)
 Fully distributed
 Able to handle large projects like Linux efficiently

14. ADVANTAGES OF GIT
▪ Performing actions other than pushing and pulling changesets is
extremely fast because the tool only needs to access the hard drive, not
a remote server.
▪ Committing new changesets can be done locally without anyone else
seeing them.
▪ Everything but pushing and pulling can be done without an internet
connection.
▪ Since each programmer has a full copy of the project repository, they
can share changes with one or two other people at a time if they want
to get some feedback before showing the changes to everyone.

15. DISADVANTAGES OF GIT
▪ There are only two major inherent disadvantages to using a distributed
system:
▪ If your project contains many large, binary files that cannot be easily
compressed, the space needed to store all versions of these files can
accumulate quickly.
▪ If your project has a very long history (50,000 changesets or more),
downloading the entire history can take an impractical amount of time
and disk space.
▪ The authors and contributors of modern distributed version control
systems are working on solving these problems, but at the moment, no
bundled, built-in features solve them.

16. WORKING WITH GIT
▪ Command line interface
▪ • Official Git Site —http://git-scm.com/

17. THANKS A LOT
Ahmed Shawky Ali El-faky