SVN 2 Git

From SVN toGit
with a pinchofGitHub
Marco De Stefano

SVN features
Centralizedversioncontrol
Commitasatomicoperation
Versioningmantainedfordirectories and file metadata
Client/Server protocolsendsdiffs
Renamingoffilescauses loss of the history
.svndirectories in the whole project
Lackof management tools (e.g. deleting part of the history)

SVN commands
>svn checkout (co)
>svncommit (ci)
>svn status (st)
>svn update
>svnrevert
>svnadd/rm
>svnadmin create
…

Centralized vs. Distributedversioncontrol
“Centralized VCS systems are designedwith the intentthatthereisOneTrue Source thatisBlessed, and thereforeGood. Alldevelopers work (checkout) fromthat source, and thenadd (commit) theirchanges, whichthenbecomesimilarlyBlessed.”
“Distributed VCS systems are designedwith the intentthatonerepositoryisasgoodasanyother, and thatmergesfromonerepositorytoanother are just anotherformofcommunication. Anysemanticvalueastowhichrepositoryshouldbetrustedisimposedfrom the outsidebyprocess, notby the software itself.”
“The realchoicebetweenusingonetype or the otherisorganizational - ifyour project or organizationwantscentralizedcontrol, then a DVCS is a non-starter. Ifyourdevelopers are expectedto work allover the country/world, withoutsecure broadband connectionsto a centralrepository, then DVCS isprobablyyoursalvation. Ifyouneedboth, you're fu***d.”

Centralized vs. Distributedversioncontrol

Gitfeatures
Distributedversioncontrol
Strong supportfornon-lineardevelopment (branches and merges)
Efficienthandlingoflargeprojects (e.g. Linux Kernel)
Pluggablemergestrategies
.git directory in project root
More disk spacerequired
Not for Windows  (but there is a native porting, msysgit)

Gitcommands
>gitinit
Creates a .gitsubdirectory in your project
Yourworking directory becomes a gitrepository
Youusegitinittomakeanexisting directory ofcontentinto a newGitrepository. You can do this in any directory at anytime, completelylocally

Gitcommands
>git clone <url> [path]
Copies a project in yourworking directory
Itcopiesall the project historylocally
Youwillget a directory with the mainbranchof the project
Youusegit clone toget a local copy of a Gitrepository

Gitcommands
>gitadd [filepattern…]
Adds file contentstoyourstaging area
Usedfornewfiles and modificationstoexistingfiles
Possibletoskipthisoperation (withcommit–aoption)
Youusegitaddto start trackingfiles and to stage changestoalreadytrackedfiles i.e. wheneveryouwantto include file changes in the nextcommit

Gitcommands
>git status [-s]
Shows the status of the files (working directory and staging area)
Givescontext and hints–displayswhich(butnothow) fileschanged
-soptiongives short output (with no hints–similartosvnst)
Youusegit statustoseeifanythinghasbeenmodified and/or stagedsince the last commit

Gitcommands
>gitdiff [--cached / HEAD] [--stat] [filepath]
Shows a patch ofcontentchangedsince last commit and notyetstaged
--cachedoptionshows the stagedchanges, HEAD showsbothstaged and unstagedchanges
--statoptiongives short output
Youusegitdifftoseehow (linebyline) fileshavebeenmodified and/or stagedsince the last commit

Gitcommands
>gitcommit [-a] [-m ‘commitmessage’]
Records a snapshotof the staging area in the currentbranch
-aoptionaddsto the snapshotall the unstagedchanges
-moptionallowstoinsert the commitmessagedirectly
Youusegitcommitto record a snapshotof the stagedchanges. Thissnapshot can thenbecompared, shared and revertedto, ifyouneedto

Gitcommands
>git reset [--hard] <HEAD/commit> [--files…]
Unstageschangesthathavebeenstaged
With --hard options, the repositorychangesto the last commit state
Possibletounstage single files
Youusegit reset HEADtounstagefilespreviouslystagedwithgitadd, toavoidincludingthem in the nextcommit

Gitcommands
>gitrm [--cached] [files…]
Removesfilesfrom the staging area – and from the working directory
--cachedoptionallowstoretain the file in the working directory
Youusegitrmtoremovefilesfrombeingtracked in Git

Gitcommands
>gitmv <source> <destination>
Has the samebehaviourof:
>gitrm--cached <source>
>mv <source> <destination>
>gitadd <destination>
Youusegitmvtorenamefiles under versioncontrol

Gitcommands
>gitbranch [-d <branchname>] [branchname]
A branchis a contextwhereyou can switch
Withoutarguments, itlists out the localbranches and points out the currentone
With a branchname, itcreates a newbranch– the default oneisnamed master
-doptionwilldeletebranchname
Youusegitbranchtolistcurrentbranches, create newbranches and deleteunnecessarybranches

Gitcommands
>git checkout [[-b] <branchname>]/ [--files…]
Swithcestobranchname
-boptionwill create branchnameand switchimmediatelytoit
--followedbyone or more files, reverts the contentofthesefilesto the last commit state
Youusegit checkout toswitchamongbranches, optionallycreatingthem; youalsouseittorevert the data ofany file to the last commit

Gitcommands
>gitmerge <branchname>
Merges the diffsbetween the currentbranch and branchnameinto the currentone
The branchbranchnamedoesn’tchange
Youusegitmergeto combine anotherbranchcontextinto the currentone

Gitcommands
>git log [--oneline] [--graph] [--decorate] [branchname]
Showscommithistoryofbranchname(the currentoneifnotspecified)
The --onelineoptionsshowsonly the first rowof the commitmessage
The --graphoptionshows a graphofbranches and merges
The --decorateoptionshows information on branchesinvolved in merges
Youusegit log tolist out the commithistory

Gitcommands
>git remote [-v] [add <url> <alias>]/[rm <alias>]
Lists the remote repositoryaliasesstored, -voptionsalsoshows the urls
Possibletohavedifferentpush and fetchurls
addallowstoadd the repository at url under the local-remotealias
rmallowstoremove the alias local-remote
Youusegit remote tolist out the remote repositories and the urlsthey’re using. You can alsoadd and removelocal-remoterepositories

Gitcommands
>gitfetch <alias/--all>
Downloadsbranches and data from a remote repository
--alloptionallowsto download data fromall remote repositories
Cannot checkout a remote repository
Youusegitfetchtosynchronizeyourrepositorywith a remote repository, fetchingall the data notalreadyexisting in yourlocalrepository

Gitcommands
>git pull <alias>/<--all>
Fetchesfrom a remote repository and triestomergeitinto the currentbranch
Has the samebehaviourof:
>gitfetch <alias>
>gitmerge <alias>
Youusegit pull tosynchronizeyourrepositorywith a remote repository, fetchingall the data notalreadyexisting in yourlocalrepository and mergingitinto the currentbranch

Gitcommands
>gitpush <alias> [branch]
Pusheslocalbranches and data to a remote repository
If no branchisspecified, the currentbranchisused
The localbranchtopushhastobe up-to-date
Youusegitpushto update a remote repositorywithchangesmadelocally

Gitcommands
>gitrevert [-n] <HEAD/commit>
Reverts the contentsof the currentbranchto the commitstate
Itmakes a newcommit on the currentbranch!
With-noptions the data isreverted and isn’tcommitted
Youusegitreverttorevert the data in the currentbranchto a specified state

Gitcommands
>gitstash <save/pop>
Allowsto record the current state of the working directory
Doesn’tmake a commit
Saveallowsto create a stash, pop puts the stashedchanges back on the working directory
Youusegitstashtotemporarilystash (and afterwordsrecover) the data in the currentbranch, e.gtoproceedwith a pull request

Tips
Enable console colors
>gitconfig --global color.diff auto
>gitconfig --global color.status auto
>gitconfig --global color.branch auto
Set name and email
>gitconfig --global user.name <Name and Surname>
>gitconfig --global user.email <email>
Set aliasesforcommands, e.g.:
>gitconfig --global alias.history ‘log --oneline--graph--decorate’
>gitconfig --global alias.st ‘status -s’
>gitconfig --global alias.ci ‘commit-m’
>gitconfig --global alias.co checkout

GitHub
Web-based hosting service for software developmentprojectsthatuseGit
Possibletohave public repositories (free iftheyrequirelessthan 300MB)

GitHub– Create a repo

GitHub– Create a repo
>mkdirhelp-example
>cd help-example
>gitinit
>touch README
>gitcommit -a –m ‘first commit’
>git remote addorigin git@github.com:tekkub/help-example.git
>gitpushorigin master

GitHub–Push data
I can’tpush, “Permissiondenied (public key)”
Topush data, youhaveto set up a pairof SSH keys, and addyour public key in the account options on GitHub
You can alsoconfigureyourGitHub account locally:
>gitconfig --global github.user <username>
>gitconfig --global github.token <token>
You can findyourtoken under yourGitHub account settings

A simple scenario
Alice createdherrepo, test, on github (seepreviousslides), containingthesefiles:
README foo.txtbar.txttest.c
Bob joinsher– and hehaswriteaccessto the repository:
>gitclone git@github.com/alice/test.git test
Bob workslocally, and makes a branch:
>cd test
>git checkout –btext-changes
Nowhehas2branches: master and text-changes

A simple scenario
Bob modifiesfoo.txt and bar.txt; afterthatheruns:
>gitaddfoo.txt
>git status –s
Mbar.txt
Mfoo.txt
The file bar.txthasbeenmodifiedbutnotalreadystaged; howeverBob runs:
>gitcommit–a–m ‘modifiedtxtfiles’
>git status –sgives no output
Thesefileshavebeenmodifiedonly in text-changesbranch

A simple scenario
Bob wantstomodifytest.c in a newbranch, withouthaving the *.txtfilesmodified
>git checkout master
>gitbranchsrc-changes
>git checkout src-changes
Bob modifies the file test.c and afterthatheruns:
>gitadd .
>gitcommit–m ‘modified test file’
Bob has3branches: master, text-changes, src-changes

A simple scenario
Meanwhile, Alice modifies README and test.c, and runs:
>gitcommit–a–m ‘modifiedreadme and test.c’
>gitpushorigin
Bob triestomergetext-changeswithsrc-changes
>gitbranch
master
* src-changes
text-changes
>gitmergetext-changes

A simple scenario
Bob triestopush the changesinto the origin
>git checkout master
>gitmergesrc-changes
>gitpushorigin
However, Bob can’tpush data to the origin, becauseheisnot up-to-date
>git pull
Whathappenswith the file test.c? BothAlice and Bob modifiedit

A simple scenario
Gittriestomergecontents– and it’sverylikelytobeableto do it
IfGit can’tmergecorrectly, Bob willsee the classicmerging style on his copy oftest.c:
<<<<<<<<< yours: test.c
//Bob’scontent
=========
//Alice’scontent
>>>>>>>>> theirs: test.c
Aftermerging, Bob can pushhis data to the origin
>gitpushorigin

What else?
Git Reference
Git Tutorial
Git User’s Manual
Pro Git Book
Git Community Book
GitHub Help
Egit - Eclipseplugin
Graphicalfrontend:
Windows, Linux (gtk), Mac OSX, Multi-platform

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SVN 2 Git

by Marco De Stefano on May 23, 2011

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SVN 2 Git — Presentation Transcript