Git is a distributed version control system (DVCS) that provides three main benefits - distributed development, non-linear workflows, and high performance. It uses a fast, efficient file-based database to track changes to files and supports branching, merging, and many non-linear workflows. Git is commonly used for both open source and private projects, with hosting options like GitHub making collaboration and code sharing easy.

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

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

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

4. ≉

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

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

8. t
Source Code Control
Gi

9. CultureChange

13. Centralized
VCS =Don’t

14. Distributed
VCS = Whatever!
Do

15. Innovate
Experiment
Safely Be Wrong
Drive-by Assist
Crowd Source

16. Crowd Source

18. Download binaries

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

20. Put it in your path

22. Identify yourself

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

24. Use it!

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

26. Just show it to me!

29. Certified
Git User

31. 145+ Commands

32. Follow the
DOTS

33. Symmetric

34. subversion server
developer A developer B

35. ch
ec
ki
n

36. te
da
up

38. n
ki
ec
ch

39. up
da
te

41. Symmetric

42. Distributed

43. developer A developer B

44. blessed repo
developer A developer B

45. commit commit
commit
commit commit
commit commit

46. delete delete

47. rebase

48. pu
sh

49. pu
sh

50. push

51. push

52. pull

53. pull

54. Distributed

55. WorkingOffline

57. More available connectivity

59. More demand to work without
connectivity

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

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

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

63. Who’s Got Git?

69. GUIs

70. GitX

71. GitSafe

72. GitK

73. GitGUI

74. EGit

76. c i a l !
O f fi
It ’s

77. UsageModels

78. Centralized
Central
Repo

79. Repo
Blessed
Dictatorship

80. Certified
Integration Managed
Development
Repo Repo

81. Mirror Mirror
Certified Development
Repo Repo
Mirrored

82. ☚ Private Public ☛
Customized
GitHub
Custom + Public Contrib

83. Hashes and Git

84. Index vs Hash
‣ Centralized VCS uses DB
sequential index.

85. Index vs Hash
‣ Git uses SHA-1 hash.

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

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

88. 40 hex characters

89. Use as little of it as is unique

90. Treeish

91. Shorthand for the hashes

92. 9AB223

93. 9AB223^

94. 9AB223..56CD77

95. HEAD

96. HEAD^

97. HEAD~3

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

99. 49
to m s
rt h a
e a

100. 46
S H A 1

101. 22
s ta rs

102. 20
g ra in s
s an d

103. 19
l is io n
c o l

104. Hashable Objects
‣ Blob
‣ Tree
‣ Commit
‣ Tag

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

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

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

108. Storage Mechanics

109. Typical SCMs use delta storage

110. CVS / Subversion / darcs / Mercurial

111. 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

112. Git uses DAG storage

113. Directed Acyclic Graph

114. Copy of the entire tree per checkin

115. cp -r srcfolder srcfolder.prev

117. Sounds inefficient...

118. zlib deflates every blob at commit

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

120. Speed

121. git: git
hg: mercurial
bzr: bazaar

122. 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

123. bazaar numbers
subversion = plus
network latency

124. 10
to
100 times
Faster

125. Location,Location,Location

126. Three Stage Thinking
of Git

127. Git
‣ git add
‣ git commit
‣ git push

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

129. Git
‣ git stash
‣ git stash apply

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

131. 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

132. 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

133. Merge & Rebase

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

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

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

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

138. Rebase for Clarity
git checkout myfeaturebranch
git rebase master

139. 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.

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

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

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

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

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

145. Sharing

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

147. 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

148. 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.

151. SVN Interop

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

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

155. Migration
‣ git svn clone

156. Migration
‣ Power off your Subversion server.

157. 3
reasons

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

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

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

162. emerging Control System
Version

163. 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

164. 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

165. 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

166. 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

167. 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/