quick intro to git
DESCRIPTION
Slides+notes for a talk on Git I did at Techmeetup Edinburgh back in January '09.TRANSCRIPT
let’s roll
GIT
Hasan Veldstra<[email protected]>
hypernumbers
Really Quick Intro To Git
quick poll: Git users, SVN users.
source control system
the logo:
an artistic impression:
like CVS or SVN, only much better. fundamental difference – distributed.
SVNCVS
SVNCVS
GIT ⋙ {
roadmap, disclaimers &c
why it’s cool, how it works, how to get started right now. basic stuff – if you like what you see, there’s lots of detailed documentation elsewhere.
i am not an expert, just sharing bits i’ve learned.
2005, to manage Linux kernel, spread fast.
Linux kernel
X11
Perl
Android
Fedora
OLPC
Ruby On Rails
WINE
VLC
Git itself
why Git?
• makes stuff cheap
why Git?
= streamlines things & encourages good practices
• makes stuff cheap• any workflow
why Git?
gets out of your way, doesn’t dictate the way you should work. use it like SVN or use it like the Linux devs.
• makes stuff cheap
• fast• any workflow
why Git?
by design & implementation (no network, speed as one of the goals, written in C by great C hackers)
from http://whygitisbetterthanx.com by Scott Chacon of GitHub
SVN is even slower than Bazaar
• makes stuff cheap
• fast• small
• any workflow
why Git?
as small or smaller than an equivalent SVN repo.
• makes stuff cheap
• fast• small
• any workflow
• easy to learn
why Git?
Git has acquired a reputation for being somewhat difficult to get started with and understand but that’s lies.
$ cd (project directory)$ git init$ (create some files)$ git add .$ git commit -m 'start the project'
distributed
distributed=
no central repository
distributed=
no central repository
(superset of SVN &c)
centralized (SVN):
repository
centralized (SVN):
repository
!
centralized (SVN):
repository
!! devs “check out” the code to create a
“working copy”
centralized (SVN):
repository
check in!
!
centralized (SVN):
repository
check in!check out
!
centralized (SVN):
repository
check in!check out
! make changes
centralized (SVN):
repository
check in!check out
! make changes
check in back to repo
centralized (SVN):
repository
check in
update
!check out! make changes
check in back to repo
centralized (SVN):repository
one-to-many relationship
centralized (SVN):repository
- - -
- -
- - - working copy #1
centralized (SVN):repository
- - -
- -
- - - working copy #2- - -
- -
- - - working copy #1
centralized (SVN):repository
- - -
- -
- - - working copy #3
- - -
- -
- - - working copy #2- - -
- -
- - - working copy #1
centralized (SVN):
• working copies are inferior
centralized (SVN):
• working copies are inferior
• & can’t talk to each other
centralized (SVN):
• working copies are inferior
• & can’t talk to each other
• you gotta be online
centralized (SVN):
• working copies are inferior
• & can’t talk to each other
• you gotta be online
• single point of failure
distributed (Git):
distributed (Git):
checkout
distributed (Git):
checkout
clonewe don’t check out, we cloneclone = full history, can do anything original can
distributed (Git):
“canonical” repository
"canonical" because it's a social convention, not a technical requirement
distributed (Git):
!
local repository #1
“canonical” repository
awesome #1
awesome #1
local commitsno network => FASTFAST => less “friction”less “friction” => encourages you to commit more often
no network => work offlinebig deal actually, i work in Starbucks a lot, actualy the reason i started using Git in the first place. also nice to be productive on trains, planes &c.
it also allows private work, so you can use your revision control system even for early drafts you don't want to publish
awesome #1
local commits#1 say you’re working on a feature, & you do the work
in several stages, over a couple of days maybe
you know, you write the first messy and inefficient version first, and then you refactor it, test it &c &c.
awesome #1
local commits#1 #2
awesome #1
local commits#1 #2 #3
with SVN you either commit all intermediate steps to the central repo, which clutters up history...
... or you don’t, in which case you’re left on your own and there is no one there to save your butt WHEN you screw up: you can’t roll back to an earlier state, you can only restore clean from the server, losing work.
this of course sucks big time.
awesome #1
local commits(& revision before pushing)
distributed (Git):
!
local repository #1
“canonical” repository
distributed (Git):
!
!
local repository #1
local repository #2
“canonical” repository
distributed (Git):
“canonical” repository
!
!
local repository #1
local repository #2
distributed (Git):
“canonical” repository
!
!
local repository #1
local repository #2= awesome
clones are full-fledged repositories => exchange patches and merge between them without touching the main repo.
several people can work together on something new amongst themselves, and then push to main when done.
staging area“canonical” repository
local repository
- - -
- -
- - - working copy
- -
-
- - -
staging area
like a shelf on which to put things that’ll make up the next commit. incremental building of. “chunk commits” = awesome. “tangled working copy” problem gone.
object database, trees & blobs that represent the repo (file contents,
stuff on your disk tracked by the repo
as many as you wantindependent of each otherprivateFAST operations (create, check out, merge, delete)
* for new ideas* for bugfixes/features* master for production, one for testing, several for day-to-day work
changes the way you workcan manage to do some of this with other systems, but is PITA.
branching
workflows
centralizedbasically like SVN but nicer
integration manager
blessed repo, integration manager, many devs.“open-source model”.
dictator&
lieutenantsfor massive projects, like Linux Kernel
infiltrationa howto
start using Git tomorrow without anyone suspecting a thing.
git-svn
$ git svn clone (URL)$ git branch bugfix-branch$ git checkout bugfix-branch(make a bunch of changes)$ git commit -m “fixed this bug”$ git rebase -i git-svn$ git checkout master$ git svn rebase$ git rebase bugfix-branch$ git svn dcommit
...all it takes
Tools• egit for Eclipse• magit for Emacs• plugins for NetBeans & Visual Studio in the works• so is a TortoiseSvn equivalent
• also Gitx on OSX, gitk on Linux• gitweb to serve repos over HTTP
Nothing is perfect
SVN handles binary files better
SVN allows partial check outs
git-scm.com#git on Freenode
github.com
MOAR:
Trac + Sourceforge + Facebook :]
Questions