Matthew McCullough's presentation of Git, the new Distributed Version Control System to the Denver Java Users Group.

1. Git going
DVCS
with
n bending
mental spoo
minutes of
90
ode control
ia source c
v
1 by Matthew McCullough of Ambient Ideas, LLC

2. “ Git
-noun sant or
unplea
Slang. an
British
”
per son
emptible
cont
ionar y
rd English Dict
-Oxfo
2

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

7. RCS
Folders

8. Clear
Source Case
Safe
CVS
PVCS
RCS
Folders

9. Subversion
BitKeeper
Perforce
Clear
Source Case
Safe
CVS
PVCS
RCS
Folders

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

11. t
Source Code Control
Gi

12. Gi
Source Code Control
t

13. CultureChange
8

22. =Don’t
Centralized
VCS

23. Innovate
16

24. Experiment
16

25. Safely Be Wrong
16

26. Drive-by Assist
16

27. Crowd Source
16

29. 18

30. 19

31. Global Git Settings
git config --global user.name quot;Hal Smithquot;
20

32. Global Git Settings
git config --global user.name quot;Hal Smithquot;
git config --global user.email quot;hal@bnl.comquot;
20

33. Global Git Settings
git config --global user.name quot;Hal Smithquot;
git config --global user.email quot;hal@bnl.comquot;
ues
val
ent
urr
tc
tpu
Ou
git config --list
20

34. Creating a Repo
mkdir myproj.git
21

35. Creating a Repo
mkdir myproj.git
cd myproj.git
21

36. Creating a Repo
mkdir myproj.git
cd myproj.git
lks!
t fo
’s i
hat
git init T
21

37. 22

38. 22

39. Who’s Got Git?
23

46. Hashes and
Integrity
28

47. 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
29

48. 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 ght
hou
It ere
‣ Blob es w
ash
h
‣ Tree
for
rds?
‣ Commit
swo
pas
‣ Tag
29

49. http://book.git-scm.com/1_the_git_object_model.html
30

50. http://book.git-scm.com/1_the_git_object_model.html
30

51. http://book.git-scm.com/1_the_git_object_model.html
30

52. http://book.git-scm.com/1_the_git_object_model.html
30

54. alized
entr
C
Alice Bob

55. alized
entr
C
Alice Bob
1 = okay.htm

56. alized
entr
C
Alice Bob
1 = okay.htm
2 = fine.htm

57. alized
entr
C
Alice Bob
1 = okay.htm
2 = fine.htm Sync

58. alized
entr
C
Alice Bob
1 = okay.htm 1 = okay.htm
2 = fine.htm 2 = fine.htm
Sync

59. alized
entr
C
Alice Bob
1 = okay.htm 1 = okay.htm
2 = fine.htm 2 = fine.htm
Sync
3 = good.htm

60. alized
entr
C
Alice Bob
1 = okay.htm 1 = okay.htm
2 = fine.htm 2 = fine.htm
Sync
3 = good.htm
3 = great.htm

61. alized
entr
C
Alice Bob
1 = okay.htm 1 = okay.htm
2 = fine.htm 2 = fine.htm
Sync
3 = good.htm
Sync
3 = great.htm

62. alized
entr
C
Alice Bob
1 = okay.htm 1 = okay.htm
2 = fine.htm 2 = fine.htm
Sync
4 = good.htm 3 = good.htm
Sync
3 = great.htm 4 = great.htm

63. alized
entr
C
Alice Bob
1 = okay.htm 1 = okay.htm
2 = fine.htm 2 = fine.htm
Sync
ERROR
4 = good.htm 3 = good.htm
ERROR
Sync
3 = great.htm 4 = great.htm

65. Distributed
Alice Bob

66. Distributed
Alice Bob
a233b76 = okay.htm

67. Distributed
Alice Bob
a233b76 = okay.htm
d234ab1 = fine.htm

68. Distributed
Alice Bob
a233b76 = okay.htm
d234ab1 = fine.htm Sync

69. Distributed
Alice Bob
a233b76 = okay.htm a233b76 = okay.htm
d234ab1 = fine.htm d234ab1 = fine.htm
Sync

70. Distributed
Alice Bob
a233b76 = okay.htm a233b76 = okay.htm
d234ab1 = fine.htm d234ab1 = fine.htm
Sync
f90b12c = good.htm

71. Distributed
Alice Bob
a233b76 = okay.htm a233b76 = okay.htm
d234ab1 = fine.htm d234ab1 = fine.htm
Sync
f90b12c = good.htm
ae42ba0 = great.htm

72. Distributed
Alice Bob
a233b76 = okay.htm a233b76 = okay.htm
d234ab1 = fine.htm d234ab1 = fine.htm
Sync
f90b12c = good.htm
Sync
ae42ba0 = great.htm

73. Distributed
Alice Bob
a233b76 = okay.htm a233b76 = okay.htm
d234ab1 = fine.htm d234ab1 = fine.htm
Sync
f90b12c = good.htm f90b12c = good.htm
Sync
ae42ba0 = great.htm ae42ba0 = great.htm

74. Hash Benefits
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.
35

75. Location,Location,Location
36

76. Remote
is like a special
Stash
Repo
Index
Working

77. Remote
is like a special
Stash
Repo
Index
Working

78. Remote
is like a special
Stash
Repo
git clone
Index
Working

79. Remote
is like a special
Stash
Repo
git clone
git checkout
Index
Working

80. Remote
is like a special
Stash
Repo
git clone
git checkout
edit some files
Index
Working

81. Remote
is like a special
Stash
Repo
git clone
git checkout
edit some files
git stash
Index
Working

82. Remote
is like a special
Stash
Repo
git clone
git checkout
edit some files
git stash
edit some files
Index
Working

83. Remote
is like a special
Stash
Repo
git clone
git checkout
edit some files
git stash
edit some files
Index git stash apply
Working

84. Remote
is like a special
Stash
Repo
git clone
git checkout
edit some files
git stash
edit some files
Index git stash apply
Working git add

85. Remote
is like a special
Stash
Repo
git clone
git checkout
edit some files
git stash
edit some files
Index git stash apply
Working git add
git commit

86. Remote
is like a special
Stash
Repo
git clone
git checkout
edit some files
git stash
edit some files
Index git stash apply
Working git add
git commit
git push

87. Remote
is like a special
Stash
Repo
git clone
git checkout
edit some files
git stash
edit some files
Index git stash apply
Working git add
git commit
git push

88. repo
uild
B
git clone git://somedomain/myproj.git
cd myproj.git
38

89. repo
uild
B
git clone git://somedomain/myproj.git
cd myproj.git
dex
te in
pda
U
git checkout master
38

90. repo
uild
B
git clone git://somedomain/myproj.git
cd myproj.git
dex
te in
pda
U
git checkout master
king
echo ‘//Comments’ >> ClassOne.java or
dit w
echo ‘//Thoughts’ >> ClassTwo.java E
38

91. repo
uild
B
git clone git://somedomain/myproj.git
cd myproj.git
dex
te in
pda
U
git checkout master
king
echo ‘//Comments’ >> ClassOne.java or
dit w
echo ‘//Thoughts’ >> ClassTwo.java E
ndex
to i
Add epo
git add ClassOne.java to r
ave
comments’ S
git commit -m’Added
38

92. repo
uild
B
git clone git://somedomain/myproj.git
cd myproj.git
dex
te in
pda
U
git checkout master
king
echo ‘//Comments’ >> ClassOne.java or
dit w
echo ‘//Thoughts’ >> ClassTwo.java E
ndex
to i
Add epo
git add ClassOne.java to r
ave
commit -m’Added comments’ S
git
ash
st
h to
stash Pus
git
38

93. Single Stage Thinking
Subversion
svn commit
‣
‣ Adds everything modified.
‣ Must list if you want specific files.
‣ What if you check in your password?
39

94. $ echo //password >> Matt1.java
$ echo //password >> Matt2.java
40

95. $ echo //password >> Matt1.java
$ echo //password >> Matt2.java
$ svn status
M Matt1.java
M Matt2.java
40

96. $ echo //password >> Matt1.java
$ echo //password >> Matt2.java
$ svn status
M Matt1.java
M Matt2.java
$ svn commit -m'Matts checkin'
Adding Matt1.java
Adding Matt2.java
Transmitting file data .
Committed revision 2.
40

97. Three Stage Thinking
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.
41

98. $ echo //SECRETPASSWORD >> mattfile1.java
$ echo //NewText2 >> mattfile2.java
42

99. $ echo //SECRETPASSWORD >> mattfile1.java
$ echo //NewText2 >> mattfile2.java
$ git status
# On branch master
# Changed but not updated:
# modified: mattfile1.txt
# modified: mattfile2.txt
42

100. $ echo //SECRETPASSWORD >> mattfile1.java
$ echo //NewText2 >> mattfile2.java
$ git status
# On branch master
# Changed but not updated:
# modified: mattfile1.txt
# modified: mattfile2.txt
dex
o in
int
Put
$ git add mattfile1.txt
42

101. $ echo //SECRETPASSWORD >> mattfile1.java
$ echo //NewText2 >> mattfile2.java
$ git status
# On branch master
# Changed but not updated:
# modified: mattfile1.txt
# modified: mattfile2.txt
dex
o in
int
Put
$ git add mattfile1.txt
epo
to r
ave
S
$ git commit -m'Matts pw checkin'
[master]: created ddcdf18: quot;Matts changesquot;
1 files changed, 1 insertions(+), 0 deletions(-)
42

102. #$%^&!
I just committed my password!
43

103. Change History
$ git reset --hard HEAD^
HEAD is now at 9de4cd3 First checkin
$ git log
commit 9de4cd3a3f24a3de3e804df84cc3321c7d0c9993
Author: Matthew McCullough
<matthewm@ambientideas.com>
Date: Wed Mar 4 23:09:17 2009 -0700
First checkin
44

104. Change History
mit
com
the
way
wa
hro
T
$ git reset --hard HEAD^
HEAD is now at 9de4cd3 First checkin
$ git log
commit 9de4cd3a3f24a3de3e804df84cc3321c7d0c9993
Author: Matthew McCullough
<matthewm@ambientideas.com>
Date: Wed Mar 4 23:09:17 2009 -0700
First checkin
44

105. Change History
mit
com
the
way
wa
hro
T
$ git reset --hard HEAD^
HEAD is now at 9de4cd3 First checkin
$ git log
commit 9de4cd3a3f24a3de3e804df84cc3321c7d0c9993
Author: Matthew McCullough
<matthewm@ambientideas.com>
Date: Wed Mar 4 23:09:17 2009 -0700
First checkin
44

106. GitMathematics
45

107. Directed Acyclic Graph
a32
2e2
8b3
4e8

108. Directed Acyclic Graph
Ann’s Feature
a32 5fa
2e2
8b3
4e8

109. Directed Acyclic Graph
Ann’s Feature
a32 5fa
2e2
8b3
4e8

110. Directed Acyclic Graph
Ann’s Feature
a32 5fa
Tim’s Feature
2e2 d19
8b3
4e8

111. Directed Acyclic Graph
Ann’s Feature
a32 5fa
Tim’s Feature
2e2 d19
Linus’ rewrite of
Tim’s feature
8b3 e69
4e8

112. Directed Acyclic Graph
Ann’s Feature
a32 5fa
Tim’s Feature
2e2 d19
Linus’ rewrite of
Tim’s feature
8b3 e69
4e8

113. WorkingOffline
47

114. Offline Anything
Checkin
48

115. Offline Anything
Checkin
Add
Branch
List change log
Grep history
Rewrite history
Stash
Merge
Label
Remove
48

116. Offline Anything
Checkin
Add
Branch
List change log
Grep history
Rewrite history
Stash
Merge
Label
Remove
practically everything but push
48

117. Offline Anything
Checkin
Add
Branch
List change log
Grep history
Rewrite history
Stash
Merge
Label
Remove
practically everything but push
48

119. Hooray! Another
checkin to my latest OSS
project!

120. Hooray! Another
checkin to my latest OSS
project!
I think I liked
subversion better...

121. UsageModels
50

122. Centralized
Central
Repo

123. Centralized
Central
Repo

124. Repo
Blessed
Dictatorship

125. Repo
Blessed
Dictatorship

126. Repo
Blessed
Dictatorship

127. Repo
Blessed
Dictatorship

128. Repo
Blessed
Dictatorship

129. Certified
Integration Managed
Development
Repo Repo

130. Certified
Integration Managed
Development
Repo Repo

131. Certified
Integration Managed
Development
Repo Repo

132. Certified
Integration Managed
Development
Repo Repo

133. Mirror Mirror
Certified Development
Repo Repo
Mirrored

134. Mirror Mirror
Certified Development
Repo Repo
Mirrored

135. Mirror Mirror
Certified Development
Repo Repo
Mirrored

136. Mirror Mirror
Certified Development
Repo Repo
Mirrored

137. Mirror Mirror
Certified Development
Repo Repo
Mirrored

138. ☚ Private Public ☛
GitHub
Custom + Public Contrib

139. ☚ Private Public ☛
GitHub
Custom + Public Contrib

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

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

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

143. Speed
56

144. 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

145. Sharing
58

146. Serving It Up
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.
59

147. 60

148. 61

149. Serving It Up
Filesystem
‣ Local folders. Yes, they can be “remotes.”
‣ Mapped network drives. Just like folders.
62

150. on
aem
it d
g
git clone git://somehost.org/myproj.git
63

151. on
aem
it d
g
git clone git://somehost.org/myproj.git
SSH
git clone mccm06@somehost.org:myproj.git
63

152. on
aem
it d
g
git clone git://somehost.org/myproj.git
SSH
git clone mccm06@somehost.org:myproj.git
TTP
H
git clone http://somehost.org/myproj.git
63

153. on
aem
it d
g
git clone git://somehost.org/myproj.git
SSH
git clone mccm06@somehost.org:myproj.git
TTP
H
git clone http://somehost.org/myproj.git
tem
sys
File
git clone ~/work/myproj.git
63

154. on
aem
it d
g
git clone git://somehost.org/myproj.git
SSH
git clone mccm06@somehost.org:myproj.git
TTP
H
git clone http://somehost.org/myproj.git
tem
sys
File
git clone ~/work/myproj.git
rive
rk d
two
Ne
git clone z:someservermyproj.git
63

155. VCS Interop
64

156. Serversion
git svn clone http://unfurl.com/trunk
git svn dcommit
‣ First class compatibility.
‣ Round trip support.
‣ Git commits = svn commits.
65

157. 66

158. GUIs
67

159. GitX
68

160. gitSafe
69

161. GitK
70

162. GitGUI
71

164. 6
reasons

165. Cherry Pick
❻
‣git cherry-pick a5b2ee
73

166. Cherry Pick
❻
‣git cherry-pick a5b2ee
‣Merge in just one commit.
73

167. Cherry Pick
❻
‣git cherry-pick a5b2ee
‣Merge in just one commit.
‣When you want a nugget, not a branchload.
73

168. Gives Credit
❺
‣Tracks who authors a change.
74

169. Gives Credit
❺
‣Tracks who authors a change.
‣“Author” even survives passing through reviewers.
74

170. Gives Credit
❺
‣Tracks who authors a change.
‣“Author” even survives passing through reviewers.
‣“Author” survives all merges.
74

171. Gives Credit
❺
‣Tracks who authors a change.
‣“Author” even survives passing through reviewers.
‣“Author” survives all merges.
‣Additionally tracks who committed a change.
74

172. Bisect Bugs
❹
‣git bisect run mvn test
75

173. Bisect Bugs
❹
‣git bisect run mvn test
‣Binary-search for bug.
75

174. Bisect Bugs
❹
‣git bisect run mvn test
‣Binary-search for bug.
‣Manual or automated modes.
75

175. Bisect Bugs
❹
‣git bisect run mvn test
‣Binary-search for bug.
‣Manual or automated modes.
‣Yak cruelty-prevention.
75

176. Squash Verbosity
❸
‣git merge --squash mybranch
76

177. Squash Verbosity
❸
‣git merge --squash mybranch
‣Reduce all your micro-checkins to block commits.
76

178. Squash Verbosity
❸
‣git merge --squash mybranch
‣Reduce all your micro-checkins to block commits.
‣Make mistakes, revise, checkin without hesitation.
76

179. 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.
76

180. Search History
❷
‣git grep SomeText HEAD^^^
77

181. Search History
❷
‣git grep SomeText HEAD^^^
‣Search in file history without checkout.
77

182. Search History
❷
‣git grep SomeText HEAD^^^
‣Search in file history without checkout.
‣Greps contents.
77

183. Rebase
❶
‣git rebase master
78

184. Rebase
❶
‣git rebase master
‣Reposition your feature branch’s start point.
78

185. Rebase
❶
‣git rebase master
‣Reposition your feature branch’s start point.
‣Makes for simpler merge graphs.
78

186. Rebase
❶
‣git rebase master
‣Reposition your feature branch’s start point.
‣Makes for simpler merge graphs.
‣Sustains feature-branch work clarity.
78

187. 79

188. Tomorrow’s VCS, Today

189. tthew
Ma
Twitter
@matthewmccull
Blog
http://www.ambientideas.com/blog
sidebar has all my social media links
Email
matthewm@ambientideas.com
GitHub
http://github.com/matthewmccullough
81

190. 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
82

191. 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
83

192. 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
84

193. 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/
85