Git Going With DVCS v1.5.2

Git going with DVCS mental spoo n bending 50 minutes of v ia source c ode control by Matthew McCullough of Ambient Ideas, LLC

What? Why? Basic Use GUI DVCS Who? Theory Sharing Interop High Points

“ Git -noun sant or Slang. an unplea British cont emptible per son ” ionar y -Oxfo rd English Dict

otistical b astard, and “ I'm an eg I name all my projects after myself. Fi rst Linux, now git. ” -Lin us Torvalds

darcs Mercurial Bazaar BitKeeper Subversion Perforce Clear Source Case Safe CVS PVCS RCS Folders

t Source Code Control Gi

CultureChange

Centralized VCS =Don’t

Distributed VCS = Whatever! Do

Innovate Experiment Safely Be Wrong Drive-by Assist Crowd Source

Crowd Source

Download binaries

Git Distro Sources Win Cygwin Win msysGit Linux Source Linux Package manager Mac MacPorts Mac git-osx-installer Any JGit

Put it in your path

Identify yourself

Global Git Settings git conﬁg --global user.name quot;Hal Smithquot; git conﬁg --global user.email quot;hal@bnl.comquot;

Use it!

Creating a Repo mkdir myproj.git cd myproj.git git init

Just show it to me!

Certified Git User

145+ Commands

Follow the DOTS

Symmetric

subversion server developer A developer B

ch ec ki n

te da up

n ki ec ch

up da te

Symmetric

Distributed

developer A developer B

blessed repo developer A developer B

commit commit commit commit commit commit commit

delete delete

rebase

Distributed

WorkingOffline

More available connectivity

More demand to work without connectivity

Offline Anything Checkin Add Branch List change log Grep history Rewrite history Stash Merge Label Remove practically everything but push

Cool! Another commit to my latest OSS project using Git! I liked subversion better...

What? Why? Basic Use GUIs DVCS Who? Theory Sharing Interop High Points

Who’s Got Git?

GitSafe

GitGUI

c i a l ! O f fi It ’s

UsageModels

Centralized Central Repo

Repo Blessed Dictatorship

Certiﬁed Integration Managed Development Repo Repo

Mirror Mirror Certiﬁed Development Repo Repo Mirrored

☚ Private Public ☛ Customized GitHub Custom + Public Contrib

Hashes and Git

Index vs Hash ‣ Centralized VCS uses DB sequential index.

Index vs Hash ‣ Git uses SHA-1 hash.

ght thou re I ashe s we h for wor ds? p ass

SHA-1 Hash ‣ Different goals. ‣ Hash for the sake of integrity. ‣ Hash for the sake of identity.

40 hex characters

Use as little of it as is unique

Treeish

Shorthand for the hashes

9AB223

9AB223^

9AB223..56CD77

HEAD~3

ve b seen B ut I’ ring new hea ash abo ut h ision s... coll

49 to m s rt h a e a

46 S H A 1

22 s ta rs

20 g ra in s s an d

19 l is io n c o l

Hashable Objects ‣ Blob ‣ Tree ‣ Commit ‣ Tag

http://book.git-scm.com/1_the_git_object_model.html

Hash Benefits Integrity ‣ Identifies damaged repos. ‣ Prevents modification of published history. ‣ Unique to file size and contents.

Hash Benefits Tags ‣ Cryptographically sign tags by GPG. ‣ Guarantee repo’s state at a point in time.

Storage Mechanics

Typical SCMs use delta storage

CVS / Subversion / darcs / Mercurial

Checkin ckin kin in Chec kin he ck ec C he in in Ch C ck k C he h ec kin C ec ec kin Delta storage gets slower Ch the Ch as history of a ﬁle gets longerin Checkin Check

Git uses DAG storage

Directed Acyclic Graph

Copy of the entire tree per checkin

cp -r srcfolder srcfolder.prev

Sounds inefﬁcient...

zlib deﬂates every blob at commit

I’ve had a 400MB Subversion repo convert to a 70MB Git repo

git: git hg: mercurial bzr: bazaar

Init Add Status Diff Branch (Cold/Hot) git hg bzr git hg bzr git hg bzr git hg bzr Tag Log Commit (Lg) Commit (Sm) git c git h hg c hg h bzr c bzr h git hg bzr git hg bzr git hg bzr git hg bzr data from http://whygitisbetterthanx.com/#git-is-fast

bazaar numbers subversion = plus network latency

10 to 100 times Faster

Location,Location,Location

Three Stage Thinking of Git

Git ‣ git add ‣ git commit ‣ git push

‣ Commits only what is added to the index. ‣ Opportunity to rewrite history locally. ‣ Provides time to change your mind. ‣ Selectively share with other repos.

Git ‣ git stash ‣ git stash apply

‣ Save work-in-progress temporarily, but safely. ‣ Merge stashed modiﬁcations back in.

Remote is like a special Stash Repo git clone git checkout edit experiment ﬁles git stash test buggy ﬁles Index git stash apply Working git add git commit git push

repo git clone git://somedomain/myproj.git B uild cd myproj.git dex pda te in git checkout master U echo ‘//Comments’ >> ClassOne.java or king echo ‘//Thoughts’ >> ClassTwo.java E dit w to i ndex git add ClassOne.java Add epo ave to r git commit -m’Added comments’ S st ash git stash Pus h to

Merge & Rebase

Cheap Branches git branch newbranch git checkout -b newer remote/branchnm

Cheap Branches git show-branch --all git branch -a

‣Local branch ‣localbranchname ‣Remote branch ‣remote/branchname

Merge Anything git merge --no-commit <sourcebranch> git merge --squash <sourcebranch> git merge <sourcebranch1> <sourcebranch2>

Rebase for Clarity git checkout myfeaturebranch git rebase master

Rebase for Clarity ‣Fast forwards the “side” branch. ‣Reposition your feature branch’s start point. ‣See “how trunk will act” before you merge. ‣Makes for simpler merge graphs. ‣Cleaner history than a merge.

ard Bra d n e ta g a32 n ch S er Master/Trunk/MainLatest d19 M 2e2 e69 8b3 erge M 9f1

Bra sing a32 n ch ba Master/Trunk/MainLatest Re 2e2 d19 8b3 e69

Master/Trunk/MainLatest a32 2e2 8b3 Bra ch n d19 e69 Rebase

a32 Master/Trunk/MainLatest 2e2 8b3 Bra n ch d19 d19 Me rg e e69 e69

What? Why? Basic Use GUIs DVCS Who? Theory Sharing Interop High Points

Sharing

Serving It Up Protocols ‣ GIT ‣ SSH ‣ SCP ‣ Local ﬁle system ‣ SAMBA ‣ HTTP ‣ WebDAV ‣ rsync

aem on git clone git://somehost.org/myproj.git g it d git clone mccm06@somehost.org:myproj.git SSH git clone http://somehost.org/myproj.git H TTP sys tem git clone ~/work/myproj.git File rk d rive Ne two git clone z:someservermyproj.git

Serving It Up ‣ git instaweb. Built in, read-only, HTTP. ‣ git daemon. Custom socket language. ‣ gitosis. Easy permissions control. ‣ github. Open source & private repos. ‣ ssh. OS controlled permissions.

SVN Interop

Subversion git svn clone http://unfurl.com/trunk git svn dcommit

Subversion ‣ First class compatibility. ‣ Round trip support. ‣ Git commits = svn commits.

Migration ‣ git svn clone

Migration ‣ Power off your Subversion server.

3 reasons

Cherry Pick ❸ ‣git cherry-pick a5b2ee ‣Merge in just one commit.

Search History ❷ ‣git grep SomeText HEAD^^^ ‣Search blob contents history without checkouts.

Bisect Bugs ❶ ‣git bisect run mvn test ‣Binary-search for bug. ‣Manual or automated modes.

emerging Control System Version

Twitter @matthewmccull Matthew Blog http://www.ambientideas.com/blog sidebar has all my social media links Email matthewm@ambientideas.com GitHub http://github.com/matthewmccullough

Resources Git Homepage http://git-scm.com Directed Acrylic Graph http://en.wikipedia.org/wiki/Directed_acyclic_graph Git for Computer Scientists http://eagain.net/articles/git-for-computer-scientists/ Git Treeish http://book.git-scm.com/4_git_treeishes.html

Resources Git Docs http://www.kernel.org/pub/software/scm/git/docs/ Git Magic eBook http://www-cs-students.stanford.edu/~blynn/gitmagic/book.pdf Linus Torvald’s Git talk at Google http://www.youtube.com/watch?v=4XpnKHJAok8 CygWin http://www.cygwin.com

Resources MSysGit http://code.google.com/p/msysgit Git Cheetah http://code.google.com/p/msysgit/wiki/GitCheetah Matthew’s Git Bookmarks http://delicious.com/matthew.mccullough/git Matthew’s Bash Prompt http://gist.github.com/47267

Image Credits ‣ http://www.ambientideasphotography.com ‣ http://flickr.com/photos/lenore-m/2903856664/ ‣ http://en.wikipedia.org/wiki/Git_(software) ‣ http://flickr.com/photos/karenhorton/1583513014/ ‣ http://flickr.com/photos/mashdnart/2545782407/ ‣ http://commons.wikimedia.org/wiki/ File:Small_Boy_nuclear_test_1962.jpg ‣ http://www.flickr.com/photos/knmurphy/2506896257/ ‣ http://www.flickr.com/photos/albyspace/1022035568/ ‣ http://flickr.com/photos/michaelhays/3070238360/ ‣ http://flickr.com/photos/d_vdm/509996632/

Git Going With DVCS v1.5.2

by Matthew McCullough on May 22, 2009

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Git Going With DVCS v1.5.2 — Presentation Transcript