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

“

”

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.name "Hal Smith"

git config --global user.email "hal@bnl.com"

Global Git Settings

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

git config --global user.email "hal@bnl.com"

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

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

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

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

BobAliceCentralized

BobAlice1 = okay.htm

Centralized

BobAlice1 = okay.htm

2 = fine.htm

Centralized

BobAlice1 = okay.htm

2 = fine.htm Sync

Centralized

BobAlice1 = okay.htm

2 = fine.htm

1 = okay.htm

2 = fine.htm Sync

Centralized

BobAlice1 = okay.htm

2 = fine.htm

3 = good.htm

1 = okay.htm

2 = fine.htm Sync

Centralized

BobAlice1 = okay.htm

2 = fine.htm

3 = good.htm

1 = okay.htm

2 = fine.htm

3 = great.htm

Sync

Centralized

BobAlice1 = okay.htm

2 = fine.htm

3 = good.htm

1 = okay.htm

2 = fine.htm

3 = great.htm

Sync

Sync

Centralized

BobAlice1 = okay.htm

2 = fine.htm

3 = good.htm

1 = okay.htm

2 = fine.htm

3 = great.htm

4 = good.htm

4 = great.htm

Sync

Sync

Centralized

BobAlice1 = okay.htm

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

BobAlicea233b76 = okay.htm

d234ab1 = fine.htm

Distributed

BobAlicea233b76 = okay.htm

d234ab1 = fine.htm Sync

Distributed

BobAlicea233b76 = okay.htm

d234ab1 = fine.htm

a233b76 = okay.htm

d234ab1 = fine.htm Sync

Distributed

BobAlicea233b76 = okay.htm

d234ab1 = fine.htm

f90b12c = good.htm

a233b76 = okay.htm

d234ab1 = fine.htm Sync

Distributed

BobAlicea233b76 = okay.htm

d234ab1 = fine.htm

f90b12c = good.htm

a233b76 = okay.htm

d234ab1 = fine.htm

ae42ba0 = great.htm

Sync

Distributed

BobAlicea233b76 = okay.htm

d234ab1 = fine.htm

f90b12c = good.htm

a233b76 = okay.htm

d234ab1 = fine.htm

ae42ba0 = great.htm

Sync

Sync

Distributed

BobAlicea233b76 = okay.htm

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

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

$ svn statusM Matt1.javaM Matt2.java

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

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

git checkout master

◀Build repo

◀Update index

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

git checkout master

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

◀Build repo

◀Update index

◀Edit working

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

git checkout master

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

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

◀Build repo

◀Update index

◀Edit working

◀Add to index

◀Save to repo

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

git checkout master

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

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

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

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

$ 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

$ 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

$ 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 <matthewm@ambientideas.com>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 <matthewm@ambientideas.com>Date: Wed Mar 4 23:09:17 2009 -0700 First checkin

Change History

◀Throw away the commit

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

$ git logcommit 9de4cd3a3f24a3de3e804df84cc3321c7d0c9993Author: Matthew McCullough <matthewm@ambientideas.com>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

Directed Acyclic Graph

a32

2e2

5fa

8b3

4e8

Ann’s Feature

Directed Acyclic Graph

a32

2e2

5fa

8b3

4e8

Ann’s Feature

Tim’s Feature

Directed Acyclic Graph

d19

a32

2e2

5fa

8b3

4e8

e69

Ann’s Feature

Tim’s Feature

Directed Acyclic Graph

Linus’ rewrite of Tim’s feature

d19

a32

2e2

5fa

8b3

4e8

e69

Ann’s Feature

Tim’s Feature

Directed Acyclic Graph

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 mccm06@somehost.org:myproj.git

◀git daemon

◀SSH

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

git clone mccm06@somehost.org:myproj.git

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

◀git daemon

◀SSH

◀HTTP

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

git clone mccm06@somehost.org:myproj.git

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

git clone ~/work/myproj.git

◀git daemon

◀SSH

◀HTTP

◀Filesystem

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

git clone mccm06@somehost.org:myproj.git

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

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

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...

Speed

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

Central Repo

Ce

nt

ra

liz

ed

Blessed Repo

Dic

ta

to

rs

hip

Blessed Repo

Dic

ta

to

rs

hip

Blessed Repo

Dic

ta

to

rs

hip

Blessed Repo

Dic

ta

to

rs

hip

Blessed Repo

Dic

ta

to

rs

hip

Certified Repo

Development Repo

Int

eg

ra

tio

n M

an

ag

ed

Certified Repo

Development Repo

Int

eg

ra

tio

n M

an

ag

ed

Certified Repo

Development Repo

Int

eg

ra

tio

n M

an

ag

ed

Certified Repo

Development Repo

Int

eg

ra

tio

n M

an

ag

ed

Mirror

Development Repo

Mir

ro

re

d

Mirror

Certified Repo

Mirror

Development Repo

Mir

ro

re

d

Mirror

Certified Repo

Mirror

Development Repo

Mir

ro

re

d

Mirror

Certified Repo

Mirror

Development Repo

Mir

ro

re

d

Mirror

Certified Repo

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

☚ P

riva

te

Pub

lic ☛

GitHub

Cu

st

om

+ P

ub

lic

Co

nt

rib

Customized

☚ P

riva

te

Pub

lic ☛

GitHub

Cu

st

om

+ P

ub

lic

Co

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rib

Customized

☚ P

riva

te

Pub

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GitHub

Cu

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+ P

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Co

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Customized

☚ P

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GitHub

GUIs

GitX

gitSafe

GitK

GitGUI

reasons6

❻‣git cherry-pick a5b2ee

Cherry Pick

❻‣git cherry-pick a5b2ee

‣Merge in just one commit.

Cherry Pick

❻‣git cherry-pick a5b2ee

‣Merge in just one commit.

‣When you want a nugget, not a branchload.

Cherry Pick

❺‣Tracks who authors a change.

Gives Credit

❺‣Tracks who authors a change.

‣“Author” even survives passing through reviewers.

Gives Credit

❺‣Tracks who authors a change.

‣“Author” even survives passing through reviewers.

‣“Author” survives all merges.

Gives Credit

❺‣Tracks who authors a change.

‣“Author” even survives passing through reviewers.

‣“Author” survives all merges.

‣Additionally tracks who committed a change.

Gives Credit

❹‣git bisect run mvn test

Bisect Bugs

❹‣git bisect run mvn test

‣Binary-search for bug.

Bisect Bugs

❹‣git bisect run mvn test

‣Binary-search for bug.

‣Manual or automated modes.

Bisect Bugs

❹‣git bisect run mvn test

‣Binary-search for bug.

‣Manual or automated modes.

‣Yak cruelty-prevention.

Bisect Bugs

❸‣git merge --squash mybranch

Squash Verbosity

❸‣git merge --squash mybranch

‣Reduce all your micro-checkins to block commits.

Squash Verbosity

❸‣git merge --squash mybranch

‣Reduce all your micro-checkins to block commits.

‣Make mistakes, revise, checkin without hesitation.

Squash Verbosity

❸‣git merge --squash mybranch

‣Reduce all your micro-checkins to block commits.

‣Make mistakes, revise, checkin without hesitation.

‣Great for SVN compatibility.

Squash Verbosity

❷‣git grep SomeText HEAD^^^

Search History

❷‣git grep SomeText HEAD^^^

‣Search in file history without checkout.

Search History

❷‣git grep SomeText HEAD^^^

‣Search in file history without checkout.

‣Greps contents.

Search History

❶‣git rebase master

Rebase

❶‣git rebase master

‣Reposition your feature branch’s start point.

Rebase

❶‣git rebase master

‣Reposition your feature branch’s start point.

‣Makes for simpler merge graphs.

Rebase

❶‣git rebase master

‣Reposition your feature branch’s start point.

‣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 matthewm@ambientideas.com

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

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