1. Understanding
git
Avik Das
Vida Engineering

2. A quick refresher on graphs
Background:

4. A
B
D C

5. A
B
D C
Nodes + Edges = Graph

6. A
B
D C
Nodes + Edges = Graph

7. A
B
D C
Nodes + Edges = Graph

8. A
B
D C
Nodes + Edges = Graph

9. A
B
D C

10. A
B
D C

11. A
B
D C
Directed Edges → Directed Graph

12. A
B
D C
Directed Edges → Directed Graph

13. A
B
D C

14. A
B
D C
cycle

15. A
B
D C

16. A
B
D C

17. A
B
D C
No cycles → Directed Acyclic Graph

18. A
B
D C
No cycles → Directed Acyclic Graph

19. A
B
D C
DAG

20. ABD C

21. ABD C
DAG → Linearizable

22. Git objects

23. BLOB

24. BLOB
def factorial(x):
if x == 0:
return 1
else:
return x *
factorial(x - 1)
print factorial(6)

25. BLOB
def factorial(x):
if x == 0:
return 1
else:
return x *
factorial(x - 1)
print factorial(6)
066681188100ef24b1ce91a3a3596baffb620051

26. BLOB
def factorial(x):
if x == 0:
return 1
else:
return x *
factorial(x - 1)
print factorial(6)
BLOB
def factorial(x):
if x == 0:
return 1
else:
return x *
factorial(x - 1)
print factorial(6)
066681188100ef24b1ce91a3a3596baffb620051 59d8c4d1b5e8561375aa819adc513529b7ea19b8

27. TREE

28. TREE
blob 5b1d3 README
tree 03e78 lib
tree cdc8b test
blob cba0a test.py
blob 911e7 xdiff

29. TREE
blob 5b1d3 README
tree 03e78 lib
tree cdc8b test
blob cba0a test.py
blob 911e7 xdiff BLOB
Lorem ipsum dolor
sit amet,
consectetur
adipiscing elit.
Morbi efficitur ex
ex, ac lobortis
velit scelerisque
BLOB
Lorem ipsum dolor
sit amet,
consectetur
adipiscing elit.
Morbi efficitur ex
ex, ac lobortis
velit scelerisque
BLOB
Lorem ipsum dolor
sit amet,
consectetur
adipiscing elit.
Morbi efficitur ex
ex, ac lobortis
velit scelerisque
TREE
blob 5b1d3 README
tree 03e78 lib
tree cdc8b test
blob cba0a test.py
blob 911e7 xdiff
TREE
blob 5b1d3 README
tree 03e78 lib
tree cdc8b test
blob cba0a test.py
blob 911e7 xdiff

30. TREE
blob 5b1d3 README
tree 03e78 lib
tree cdc8b test
blob cba0a test.py
blob 911e7 xdiff BLOB
Lorem ipsum dolor
sit amet,
consectetur
adipiscing elit.
Morbi efficitur ex
ex, ac lobortis
velit scelerisque
BLOB
Lorem ipsum dolor
sit amet,
consectetur
adipiscing elit.
Morbi efficitur ex
ex, ac lobortis
velit scelerisque
BLOB
Lorem ipsum dolor
sit amet,
consectetur
adipiscing elit.
Morbi efficitur ex
ex, ac lobortis
velit scelerisque
TREE
blob 5b1d3 README
tree 03e78 lib
tree cdc8b test
blob cba0a test.py
blob 911e7 xdiff
TREE
blob 5b1d3 README
tree 03e78 lib
tree cdc8b test
blob cba0a test.py
blob 911e7 xdiff
ac72efa71e90424bdb41dc795609d572ddd88643

31. COMMIT

32. COMMIT
tree ac72e
parent 84ce1
author Avik Das
committer Avik Das
Commit message

33. COMMIT
tree ac72e
parent 84ce1
author Avik Das
committer Avik Das
Commit message
COMMIT
tree ac72e
parent 84ce1
author Avik Das
committer Avik Das
Commit message

34. COMMIT
tree ac72e
parent 84ce1
author Avik Das
committer Avik Das
Commit message
COMMIT
tree ac72e
parent 84ce1
author Avik Das
committer Avik Das
Commit message
TREE
blob 5b1d3 README
tree 03e78 lib
tree cdc8b test
blob cba0a test.py
blob 911e7 xdiff

35. COMMIT
tree ac72e
parent 84ce1
author Avik Das
committer Avik Das
Commit message
COMMIT
tree ac72e
parent 84ce1
author Avik Das
committer Avik Das
Commit message
TREE
blob 5b1d3 README
tree 03e78 lib
tree cdc8b test
blob cba0a test.py
blob 911e7 xdiff
3f34c01a210400daf86c479b243fe50078c279c1

36. Working directory → staging → repository

37. C3C1 C2
HEAD
master
STAGING/INDEXWORKING DIRECTORY COMMANDS
origin/master

38. C3C1 C2
HEAD
master
STAGING/INDEXWORKING DIRECTORY
README (V1)
COMMANDS
vim README
origin/master

39. C3C1 C2
HEAD
master
STAGING/INDEXWORKING DIRECTORY
README (V1)
COMMANDS
vim README
git add README
origin/master

40. C3C1 C2
HEAD
master
STAGING/INDEXWORKING DIRECTORY
README (V1)
COMMANDS
vim README
git add README
vim README
README (V2)
origin/master

41. C3C1 C2
HEAD
master
STAGING/INDEXWORKING DIRECTORY
README (V2)
COMMANDS
vim README
git add README
vim README
git add README
origin/master

42. C3C1 C2
HEAD
master
STAGING/INDEXWORKING DIRECTORY
README (V2)
COMMANDS
vim README
git add README
vim README
git add README
vim READMEREADME (V3)
origin/master

43. C3C1 C2
HEAD
master
STAGING/INDEXWORKING DIRECTORY
README (V2)
COMMANDS
git diff # between V2 and V3
README (V3)
origin/master

44. C3C1 C2
HEAD
master
STAGING/INDEXWORKING DIRECTORY
README (V2)
COMMANDS
git diff # between V2 and V3
git diff --staged # between V2
# and empty
README (V3)
origin/master

45. C3C1 C2
HEAD
STAGING/INDEXWORKING DIRECTORY COMMANDS
git commit
README (V3)
C4
masterorigin/master

46. C3C1 C2
HEAD
STAGING/INDEXWORKING DIRECTORY COMMANDS
git commit
git push
# or git push origin master
README (V3)
C4
masterorigin/master

47. Branching

48. A B
git clone <url>
origin/master
master
HEAD

49. A B
git clone <url>
git pull
origin/master
master
HEAD
C

50. A B
git clone <url>
git pull
git checkout -b mine
origin/master
master
HEAD
C
mine

51. A B
git clone <url>
git pull
git checkout -b mine
git commit
origin/master
master
HEAD
C
mine
X

52. A B
git clone <url>
git pull
git checkout -b mine
git commit
git commit
origin/master
master
HEAD
C
mine
X Y

53. A B
git clone <url>
git pull
git checkout -b mine
git commit
git commit
git checkout master
origin/master
master
C
mine
X Y
HEAD

54. A B
git clone <url>
git pull
git checkout -b mine
git commit
git commit
git checkout master
git pull
origin/mastermaster
C
mine
X Y
HEAD
D E

55. A B
git clone <url>
git pull
git checkout -b mine
git commit
git commit
git checkout master
git pull
git checkout mine
origin/mastermaster
C
mine
X Y
D E
HEAD

56. A B
git clone <url>
git pull
git checkout -b mine
git commit
git commit
git checkout master
git pull
git checkout mine
git merge master
origin/mastermaster
C
X Y
D E
M
mine HEAD

57. A B
git clone <url>
git pull
git checkout -b mine
git commit
git commit
git checkout master
git pull
git checkout mine
git merge master
git commit
origin/mastermaster
C
X Y
D E
M Z
mine HEAD

58. A B
git clone <url>
git pull
git checkout -b mine
git commit
git commit
git checkout master
git pull
git checkout mine
origin/mastermaster
C
mine
X Y
D E
HEAD

59. A B
git clone <url>
git pull
git checkout -b mine
git commit
git commit
git checkout master
git pull
git checkout mine
git rebase master
origin/mastermaster
C
X Y
D E
X’
mine
Y’
HEAD

60. A B
git clone <url>
git pull
git checkout -b mine
git commit
git commit
git checkout master
git pull
git checkout mine
git rebase master
git commit
origin/mastermaster
C
X Y
D E
X’ Y’
mine
Z
HEAD

61. A B
git clone <url>
git pull
git checkout -b mine
git commit
git commit
git checkout master
git pull
git checkout mine
git rebase master
git commit
origin/mastermaster
C
X Y
D E
X’ Y’
mine
Z
HEADOnly reachable by SHA1

62. Rewriting history

63. A B
master
C1 C2 C3 C4 C5
mine

64. A B
master
C1 C2 C3 C4 C5
mine
Main changes, split upover two WIP commits

65. A B
master
C1 C2 C3 C4 C5
mine
Main changes, split upover two WIP commits
Needs some
minor touch ups

66. A B
master
C1 C2 C3 C4 C5
mine
Main changes, split upover two WIP commits
Needs some
minor touch ups
Not actually
needed anymore

67. A B
master
C1 C2 C3 C4 C5
mine
Main changes, split upover two WIP commits
Needs some
minor touch ups
Commit message
needs work
Not actually
needed anymore

68. A B
master
C1 C2
git rebase -i master
C3 C4 C5
mine
Main changes, split upover two WIP commits
Needs some
minor touch ups
Commit message
needs work
Not actually
needed anymore

69. pick 8af53d3 main feature WIP
pick 76d8150 Refactor
pick dd69f0c main feature WIP 2
pick 974b13e On second thought, not needed
pick 508fe0d Build on top of refactor

70. pick 8af53d3 main feature WIP
pick 76d8150 Refactor
pick dd69f0c main feature WIP 2
pick 974b13e On second thought, not needed
pick 508fe0d Build on top of refactor

71. pick 8af53d3 main feature WIP
pick 76d8150 Refactor
pick dd69f0c main feature WIP 2
pick 508fe0d Build on top of refactor

72. pick 8af53d3 main feature WIP
pick 76d8150 Refactor
pick dd69f0c main feature WIP 2
pick 508fe0d Build on top of refactor

73. pick 8af53d3 main feature WIP
pick dd69f0c main feature WIP 2
pick 76d8150 Refactor
pick 508fe0d Build on top of refactor

74. pick 8af53d3 main feature WIP
squash dd69f0c main feature WIP 2
pick 76d8150 Refactor
pick 508fe0d Build on top of refactor

75. pick 8af53d3 main feature WIP
squash dd69f0c main feature WIP 2
edit 76d8150 Refactor
pick 508fe0d Build on top of refactor

76. pick 8af53d3 main feature WIP
squash dd69f0c main feature WIP 2
edit 76d8150 Refactor
reword 508fe0d Build on top of refactor

77. # This is a combination of 2 commits
# The first commit's message is:
main feature WIP
# This is the 2nd commit's message:
main feature WIP
# Please enter the commit message for your changes.
SQUASH

78. Implement main feature
Usual explanation
# Please enter the commit message for your changes.
SQUASH

79. Stopped at 56b3bb2562e9ee1a0a984b45e7f2220f1148d189... To be edited
You can amend the commit now, with
git commit --amend
Once you are satisfied with your changes, run
git rebase --continue
EDIT

80. Build on top of refactor
# Please enter the commit message for your changes.
REWORD

81. Build on top of refactor
Add some clarifying explanation.
# Please enter the commit message for your changes.
REWORD

82. A B
master
C1 C2 C3 C4 C5
mine

83. A B
master
C1 C2 C3 C4 C5
X C2’ C5’
mine

84. A B
master
C1 C2 C3 C4 C5
X C2’ C5’
mine
Combination ofcommits C1 + C3

85. A B
master
C1 C2 C3 C4 C5
X C2’ C5’
mine
Combination ofcommits C1 + C3
Edited from C2

86. A B
master
C1 C2 C3 C4 C5
X C2’ C5’
mine
Combination ofcommits C1 + C3
Edited from C2
Reworded from C5

87. A B
master
C1 C2
git push --force
C3 C4 C5
X C2’ C5’
mine
Combination ofcommits C1 + C3
Edited from C2
Reworded from C5

88. git-rev-parse

89. git rev-parse HEAD

90. git rev-parse HEAD
git rev-parse HEAD^

91. git rev-parse HEAD
git rev-parse HEAD^
git rev-parse HEAD^^

92. git rev-parse HEAD
git rev-parse HEAD^
git rev-parse HEAD^^
git rev-parse HEAD^^^

93. git rev-parse HEAD^^^

94. git rev-parse HEAD~3

95. git rev-parse master

96. git rev-parse master
git rev-parse master^

97. git rev-parse 757e4cf

98. Other useful commands

99. git show
git show <ref>

100. git reset
git reset --hard
git reset --soft

101. git add -p

102. git log <ref>

103. git reflog

104. git config

105. git <verb> --help
git help <verb>
man git-<verb>

106. Questions?