git the fast version control system

GitThe fast version control system

Jeroen Rosenberg [email protected]

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Git - the fast version control system

Table of contents

Short introduction to version control Version control systems Comparison with subversion Distributed version control Git usage

Basic operations Solving conflicts Branching as a core concept

Tooling Conclusion


Version controlShort introduction


Version control (1)

The management of changes to documents, programs, and other information stored as computer files

A system that maintains versions of files at progressive stages of development.

Every file Has a full history of changes Can be restored to any version

A communication tool, like email, but with code rather than human conversation


Version control (2)

Benefits


Version control (2)

Benefits Allows a team to share code


Version control (2)

Benefits Allows a team to share code Maintains separate “production”

versions of code that are always deployable


Version control (2)



Allows simultaneous development of different features on the same codebase


Version control (2)




Keeps track of all old versions of files


Version control (2)




Keeps track of all old versions of files Prevents work being overwritten


GlossarySome commonly used terms explained before moving

on


Key terms in version control Branch a copy of a set of files under version control which

may be developed at different speeds or in different ways

Checkout to copy the latest version of (a file in) the repository to your working copy

Commit to copy (a file in) your working copy back into the repository as a new version

Merge to combine multiple changes made to different working copies of the same files in the repository

Repository a (shared) database with the complete revision history of all files under version control

Trunk the unique line of development that is not a branch

Update to retrieve and integrate changes in the repository since the update.

Working copy your local copies of the files under version control you want to edit


Version control systems


Very limited and inflexible

Concurrent Versions System (CVS)




Fills most of the holes found in CVS, but added nothing to its development model

Subversion (SVN)




Fills most of the holes found in CVS, but added nothing to its development model

Subversion (SVN)

More feature rich and functional

Git


Comparison with SVN

Subversion Git


Comparison with SVN

Subversion Centralized

Git Distributed


Comparison with SVN

Subversion Centralized Branching can be a pain and

is used sparingly

Git Distributed Branching is very easy and

is a core concept


Comparison with SVN


is used sparingly Conflicts frequently occur

and renaming is not handled well


is a core concept Conflicts occur less frequent,

renaming is properly handled


Comparison with SVN




Can be slow due to network latency




Very fast since less operations involve network latency


Comparison with SVN




Can be slow due to network latency

Can consume quite some disk space




Very fast since less operations involve network latency

Consumes 30 times less disk space


Distributed version control

The new generation of version control


A basic, centralized version control systemUsers commit changes to the central repository and a new version is born to be checked out by other users


A distributed version control systemEach user has a full local copy of the repository. Users commit changes and when they want to share it, the push it to the shared repository


Git usageBasic operations


Tracking a project..

SVN Git$ svn checkout url

$ git clone url




$ git clone url

Mirror the central server

Anything the main repository can do, you can do!




$ git clone url

My project is tiny - git is overkill“Why would I carry a Swiss knife when I only want to open cans?”




$ git clone url

Tiny projects should be scalable too!“You wouldn’t use Roman digits just because you perform calculations with small numbers, now would you?”

Tiny projects may grow beyond your expectations“One day you’ll desperately need that hex wrench and you’re stuck with your plain can-opener”



SVN Git$ svn checkout url $ git clone url$ svn update $ git pull$ svn add file $ git add file$ svn rm file $ git rm file$ svn mv file $ git mv file$ svn commit $ git commit –a$ svn revert path $ git checkout

pathPretty straightforwarded, huh?


Advanced committing…

SVN Git… …$ svn mv file $ git mv file$ svn commit $ git commit –a$ svn revert path $ git checkout

pathWhat if you screw up?# re-edit the metadata and update the tree$ git commit --amend

or

# toss your latest commit away without changing the working tree$ git reset HEAD^


Solving conflictsInstant merging


Closer look at pulling..

SVN Git$ svn checkout url $ git clone url$ svn update $ git pull$ svn add file $ git add file… …


Auto-merging..


What actually happens…

# Fetch latest changes from origin$ git fetch

# Merge fetched changes into current branch$ git merge refs/heads/master


Auto-merging..


What actually happens…

Recursive merge strategy – create a merged reference tree of common ancestors for three-way merge

fewer merge conflicts can detect and handle renames


Resolving conflicts..


Suppose Jeff and Dan both made changes to the same line in file…

CONFLICT (content): Merge conflict in fileAutomatic merge failed; fix conflicts and then commit the result.

Uh oh…. now what?




Well, just merge manually…

# run your favourite file merge application$ git mergetool –t opendiff

Git - the fast version control system source: http://gitguru.com




…and commit!

# commit to resolve the conflict$ git commit


BranchingA core concept


Creating a branch..

SVN Git$ svn copy url_of_trunk url_of_branch

$ svn switch url_of_branch

$ git branch name_of_branch

$ git checkout name_of_branch


Creating a branch..

SVN Git$ svn copy url_of_trunk url_of_branch

$ svn switch url_of_branch

$ git branch name_of_branch

$ git checkout name_of_branch

Or create and switch to a branch based on another branch

$ git checkout –b new_branch other_branch


Some common scenarios…Why would I require branching?


Scenario 1 – Interrupted workflowYou’re finished with part 1 of a new feature but you can’t continue with part 2 before part 1 is released and tested


Scenario 2 – Quick fixesWhile you’re busy implementing some feature suddenly you’re being told to drop everything and fix a newly discovered bug


Git usage overview

Just to summarize…


Git command sequence

Source: http://git.or.cz


ToolingStuck at ‘Ye Olde Terminal’? Not necessarily…


Git UI front-ends


OpenInGitGuiFinder extension



TortoiseGit

Git Extensions

Windows Explorer extensions



TortoiseGit

Git Extensions

Windows Explorer extensions

JGit / EGitEclipse integration


ConclusionWhy switch to Git?


Reasons to switch to Git

Endless, easy, non-file-system-based, local branches

Enhanced merging strategy Performance Advanced features enable better

workflow Stashing temporary work Collaboration before public commits


Closing and Q&A

References Git: http://git-scm.com/download Git Docs:

http://git-scm.com/documentation GitX: http://gitx.frim.nl/ TortoiseGit:

http://code.google.com/p/tortoisegit/ Git Extensions:

http://sourceforge.net/projects/gitextensions/

JGit / EGit: http://www.eclipse.org/egit/

http://git-scm.com/download

http://git-scm.com/documentation

http://code.google.com/p/tortoisegit/



http://www.eclipse.org/egit/

git the fast version control system

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