git going with dvcs v1.3

by Matthew McCullough of Ambient Ideas, LLC

with DVCSGit going

90 minutes of mental spoon bending

via source code control

Git-nounBritish Slang. an unpleasant or

contemptible person

-Oxford English Dictionary

“

”

I'm an egotistical bastard, and

I name all my projects

after myself. First Linux,

now git.-Linus Torvalds

“

”

http://en.wikipedia.org/wiki/Linux

























RCS

Folders

CVSPVCS

ClearCaseSource

Safe

RCS

Folders

CVS

BitKeeperSubversion

PVCS

PerforceClearCaseSource

Safe

RCS

Folders

CVS

BitKeeperSubversion

PVCS

PerforceClearCaseSource

Safe

Mercurial

Bazaar

RCS

Folders

darcs

GitSource Code Control

Git Source Code Control

CultureChange

CentralizedVCS =Don’t

Innovate

Experiment

Safely Be Wrong

Drive-by Assist

Crowd Source

git config --global user.name "Hal Smith"

Global Git Settings


git config --global user.email "[email protected]"

Global Git Settings


git config --global user.email "[email protected]"

git config --list

Global Git Settings

◀Output current values

mkdir myproj.git

Creating a Repo

mkdir myproj.git

cd myproj.git

Creating a Repo

mkdir myproj.git

cd myproj.git

git init ◀That’s it folks

!

Creating a Repo

Who’s Got Git?

Hashes andIntegrity

Index vs. Hash‣ Centralized VCS uses DB auto-increment index.‣ Git uses SHA-1 hash.‣ Hash for the sake of integrity.

Hashable Objects‣ Blob‣ Tree‣ Commit‣ Tag

SHA-1 Hash

Index vs. Hash‣ Centralized VCS uses DB auto-increment index.‣ Git uses SHA-1 hash.‣ Hash for the sake of integrity.

Hashable Objects‣ Blob‣ Tree‣ Commit‣ Tag

SHA-1 Hash

I thought

hashes were

for

passwords?

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

BobAliceCentralized

BobAlice1 = okay.htm

Centralized


2 = fine.htm

Centralized


2 = fine.htm Sync

Centralized


2 = fine.htm

1 = okay.htm

2 = fine.htm Sync

Centralized


2 = fine.htm

3 = good.htm

1 = okay.htm

2 = fine.htm Sync

Centralized


2 = fine.htm

3 = good.htm

1 = okay.htm

2 = fine.htm

3 = great.htm

Sync

Centralized


2 = fine.htm

3 = good.htm

1 = okay.htm

2 = fine.htm

3 = great.htm

Sync

Sync

Centralized


2 = fine.htm

3 = good.htm

1 = okay.htm

2 = fine.htm

3 = great.htm

4 = good.htm

4 = great.htm

Sync

Sync

Centralized


2 = fine.htm

3 = good.htm

1 = okay.htm

2 = fine.htm

3 = great.htm

4 = good.htm

4 = great.htm

Sync

Sync

Centralized

ERRORERROR

BobAliceDistributed

BobAlicea233b76 = okay.htm

Distributed


d234ab1 = fine.htm

Distributed


d234ab1 = fine.htm Sync

Distributed


d234ab1 = fine.htm

a233b76 = okay.htm


Distributed


d234ab1 = fine.htm

f90b12c = good.htm

a233b76 = okay.htm


Distributed


d234ab1 = fine.htm

f90b12c = good.htm

a233b76 = okay.htm

d234ab1 = fine.htm

ae42ba0 = great.htm

Sync

Distributed


d234ab1 = fine.htm

f90b12c = good.htm

a233b76 = okay.htm

d234ab1 = fine.htm

ae42ba0 = great.htm

Sync

Sync

Distributed


d234ab1 = fine.htm

f90b12c = good.htm

a233b76 = okay.htm

d234ab1 = fine.htm

ae42ba0 = great.htm ae42ba0 = great.htm

f90b12c = good.htm

Sync

Sync

Distributed

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

Tags‣ Cryptographically sign tags by GPG/email.

Independence‣ Separation from sequence # of checkin.

Hash Benefits

Location,Location,Location

Subversion‣ svn commit‣ Adds everything modified.‣ Must list if you want specific files.‣ What if you check in your password?

Single Stage Thinking

$ echo //password >> Matt1.java$ echo //password >> Matt2.java


$ svn statusM Matt1.javaM Matt2.java


$ svn statusM Matt1.javaM Matt2.java

$ svn commit -m'Matts checkin'Adding Matt1.javaAdding Matt2.javaTransmitting file data .Committed revision 2.

Repo

is like a special

IndexWorking

Stash Rem

ote

Repo

is like a special

IndexWorking

Stash

git clone

Rem

ote

Repo

is like a special

IndexWorking

Stash

git clone

git checkout

Rem

ote

Repo

is like a special

IndexWorking

Stash

git clone

git checkout

edit some files

Rem

ote

Repo

is like a special

IndexWorking

Stash

git clone

git checkout

edit some files

git stash

Rem

ote

Repo

is like a special

IndexWorking

Stash

git clone

git checkout

edit some files

git stash

edit some files

Rem

ote

Repo

is like a special

IndexWorking

Stash

git clone

git checkout

edit some files

git stash

edit some files

git stash apply

Rem

ote

Repo

is like a special

IndexWorking

Stash

git clone

git checkout

edit some files

git stash

edit some files

git stash apply

git add

Rem

ote

Repo

is like a special

IndexWorking

Stash

git clone

git checkout

edit some files

git stash

edit some files

git stash apply

git add

git commit

Rem

ote

Repo

is like a special

IndexWorking

Stash

git clone

git checkout

edit some files

git stash

edit some files

git stash apply

git add

git commit

Rem

ote

git push

git clone git://somedomain/myproj.gitcd myproj.git

◀Build repo


git checkout master

◀Build repo

◀Update index


git checkout master

echo ‘//Comments’ >> ClassOne.javaecho ‘//Thoughts’ >> ClassTwo.java

◀Build repo

◀Update index

◀Edit working


git checkout master


git add ClassOne.javagit commit -m’Added comments’

◀Build repo

◀Update index

◀Edit working

◀Add to index

◀Save to repo


git checkout master


git add ClassOne.javagit commit -m’Added comments’

git stash

◀Build repo

◀Update index

◀Edit working

◀Add to index

◀Save to repo

◀Push to stash

Git‣ git add‣ git commit‣ git push‣ Commits only what is added to the index.‣ Opportunity to change history locally.‣ Selectively share with other repos.

Three Stage Thinking

$ echo //SECRETPASSWORD >> mattfile1.txt$ echo //NewText2 >> mattfile2.txt


$ git status# On branch master# Changed but not updated:# modified: mattfile1.txt# modified: mattfile2.txt



$ git add mattfile1.txt ◀Put into index



$ git add mattfile1.txt

$ git commit -m'Matts pw checkin'[master]: created ddcdf18: "Matts changes" 1 files changed, 1 insertions(+), 0 deletions(-)

◀Put into index

◀Save to repo

#$%^&!I just committed my password!

$ git reset --hard HEAD^HEAD is now at 9de4cd3 First checkin

$ git logcommit 9de4cd3a3f24a3de3e804df84cc3321c7d0c9993Author: Matthew McCullough <[email protected]>Date: Wed Mar 4 23:09:17 2009 -0700 First checkin

Change History

$ git reset --hard HEAD^HEAD is now at 9de4cd3 First checkin

$ git logcommit 9de4cd3a3f24a3de3e804df84cc3321c7d0c9993Author: Matthew McCullough <[email protected]>Date: Wed Mar 4 23:09:17 2009 -0700 First checkin

Change History

◀Throw away the commit

GitMathematics

a32

2e2

8b3

4e8

Directed Acyclic Graph

a32

2e2

5fa

8b3

4e8

Ann’s Feature


a32

2e2

5fa

8b3

4e8

Ann’s Feature

Tim’s Feature


d19

a32

2e2

5fa

8b3

4e8

e69

Ann’s Feature

Tim’s Feature


Linus’ rewrite of Tim’s feature

d19

Sharing

Network‣ 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.

Serving It Up

Filesystem‣ Local folders. Yes, they can be “remotes.”

‣ Mapped network drives. Just like folders.

Serving It Up

git clone git://somehost.org/myproj.git ◀git daemon

git clone git://somehost.org/myproj.git

git clone [email protected]:myproj.git

◀git daemon

◀SSH



git clone http://somehost.org/myproj.git

◀git daemon

◀SSH

◀HTTP




git clone ~/work/myproj.git

◀git daemon

◀SSH

◀HTTP

◀Filesystem




git clone ~/work/myproj.git

git clone z:\someserver\myproj.git

◀git daemon

◀SSH

◀HTTP

◀Filesystem

◀Network drive

Merge & Rebase

Cheap Branches

git show-branch --allgit branch -a

‣Local branch‣localbranchname‣Remote‣remote/branchname

Cheap Branches

Merge Anything

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

‣Selectable merge strategy‣Octopus: More than one ‣Review before committing‣Flatten micro-checkins

Merge Anything

Merge Strategies

Rebase for Clarity

git checkout myfeaturebranchgit rebase master

‣Cleaner history than a merge‣Fast forwards original branch‣Lets you see “how trunk will act” before you merge

Rebase for Clarity

WorkingOffline

Checkin

Offline Anything

CheckinAddBranchList change logGrep historyRewrite historyStashMergeLabelRemove

Offline Anything

CheckinAddBranchList change logGrep historyRewrite historyStashMergeLabelRemovepractically everything but push

Offline Anything

Hooray! Another checkin to my latest OSS

project!

Hooray! Another checkin to my latest OSS

project!

I think I liked subversion better...

data from http://whygitisbetterthanx.com/#git-is-fast

git hg bzr

Init

git hg bzr

Add

git hg bzr

Status

git hg bzr

Diff

git hg bzr

Tag

git hg bzr

Log

git hg bzr

Commit (Lg)

git hg bzr

Commit (Sm)

git c git h hg c hg h bzr c bzr h

Branch (Cold/Hot)

VCS Interop

git svn clone http://unfurl.com/trunkgit svn dcommit

‣ First class compatibility.

‣ Round trip support.

‣ Git commits = svn commits.

Subversion

UsageModels

Central Repo

Ce

nt

ra

liz

ed

Blessed Repo

Dic

ta

to

rs

hip

Certified Repo

Development Repo

Int

eg

ra

tio

n M

an

ag

ed

Mirror

Development Repo

Mir

ro

re

d

Mirror

Certified Repo

Cu

st

om

+ P

ub

lic

Co

nt

rib

☚ P

riva

te

Pub

lic ☛

GitHub

Cu

st

om

+ P

ub

lic

Co

nt

rib

Customized

☚ P

riva

te

Pub

lic ☛

GitHub

gitSafe

GitGUI

reasons6

❻‣git cherry-pick a5b2ee

Cherry Pick


‣Merge in just one commit.

Cherry Pick


‣Merge in just one commit.

‣When you want a nugget, not a branchload.

Cherry Pick

❺‣Tracks who authors a change.

Gives Credit


‣“Author” even survives passing through reviewers.

Gives Credit



‣“Author” survives all merges.

Gives Credit



‣“Author” survives all merges.

‣Additionally tracks who committed a change.

Gives Credit

❹‣git bisect run mvn test

Bisect Bugs


‣Binary-search for bug.

Bisect Bugs



‣Manual or automated modes.

Bisect Bugs



‣Manual or automated modes.

‣Yak cruelty-prevention.

Bisect Bugs

❸‣git merge --squash mybranch

Squash Verbosity


‣Reduce all your micro-checkins to block commits.

Squash Verbosity



‣Make mistakes, revise, checkin without hesitation.

Squash Verbosity



‣Make mistakes, revise, checkin without hesitation.

‣Great for SVN compatibility.

Squash Verbosity

❷‣git grep SomeText HEAD^^^

Search History


‣Search in file history without checkout.

Search History


‣Search in file history without checkout.

‣Greps contents.

Search History

❶‣git rebase master

Rebase


‣Reposition your feature branch’s start point.

Rebase



‣Makes for simpler merge graphs.

Rebase



‣Makes for simpler merge graphs.

‣Sustains feature-branch work clarity.

Rebase

Tomorrow’s VCS, Today

MatthewTwitter @matthewmccull

Blog http://www.ambientideas.com/blog sidebar has all my social media links

Email [email protected]

GitHub http://github.com/matthewmccullough

Git Homepagehttp://git-scm.com

Directed Acrylic Graphhttp://en.wikipedia.org/wiki/Directed_acyclic_graph

Git for Computer Scientistshttp://eagain.net/articles/git-for-computer-scientists/

Git Treeishhttp://book.git-scm.com/4_git_treeishes.html

Resources

http://en.wikipedia.org/wiki/Directed_acyclic_graph




Git Docshttp://www.kernel.org/pub/software/scm/git/docs/

Git Magic eBookhttp://www-cs-students.stanford.edu/~blynn/gitmagic/book.pdf

Linus Torvald’s Git talk at Googlehttp://www.youtube.com/watch?v=4XpnKHJAok8

CygWinhttp://www.cygwin.com

Resources

MSysGithttp://code.google.com/p/msysgit

Git Cheetahhttp://code.google.com/p/msysgit/wiki/GitCheetah

Matthew’s Git Bookmarkshttp://delicious.com/matthew.mccullough/git

Matthew’s Bash Prompthttp://gist.github.com/47267

Resources

‣ 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/

Image Credits

git going with dvcs v1.3

Education