Introduction into Git Version Management System Git graph functionality Git in the SAP World abapGit - Open Source ABAP Git solution

1. What the Git?
Hendrik Neumann

2. 2
What the Git?
Answer in 5 steps:
1. Git and version control
2. Git internals
3. Git working
4. Git in the world of SAP
5. Git and ABAP
Agenda

3. Version Control

4. 4
File revision hell…
Example1:
Example2:
 Version Control Systems to the rescue

5. 5
Version control is a system that records
changes to a file or set of files over time so that
you can recall specific versions later.
Definition
Quelle: ProGit, 2nd edition by Chacon & Straub

6. 6
Local Computer
Local version control
Version Database
File Version 3
Version 2
Version 1
Checkout

7. 7
Source Code Control System (SCCS)
• early 1970s by M. J. Rochkind
• repository with file locking: check out with/without lock
Revision Control System (RCS)
• early 1980s by Walter F. Tichy
• forward and reverse delta concepts for the efficient storage of
different file revision
Local version control

8. 8
Centralized version control
Computer A Central VCS Server
Version Database
File
Version 3
Version 2
Version 1
Computer B
File

9. 9
Concurrent Version System (CVS)
• 1986 by Dick Grune
• CVS gave each developer write permission in his or her private
working copy
• automatic merge of changes by different developers unless the
same line was changed  conflict
Subversion (SVN)
• 2001
• committed changes atomically and had significantly better support
for branches
Centralized version control

10. 10
Distributed version control
Server Computer
Version Database
Version 3
Version 2
Version 1
Computer B
Version Database
Version 3
Version 2
Version 1
File
Computer A
Version Database
Version 3
Version 2
Version 1
File

11. 11
BitKeeper and Mercurial
• no central repository
• provide each developer with his own
copy
Mercurial and Monotone
• use hash fingerprints to uniquely identify
a file’s content
Distributed version control

12. 12
Linux kernel project
• 1991–2002: patches and archived files by email
• 2002: BitKeeper
• 2005: BitKeeper no longer usable free of charge
• April 2005: Linus Torvalds started Git
• Starting April 20 Linux kernel project uses Git (6,7 million lines of
code!)
Git has evolved and matured to be
• easy to use
• incredibly fast
• efficient with large projects
• incredible branching system for non-linear development.
The history of Git

13. 13
Git became self-hosted on April 7 with this commit:
Git‘s birth
commit e83c5163316f89bfbde7d9ab23ca2e25604af29
Author: Linus Torvalds <torvalds@ppc970.osdl.org>
Date: Thu Apr 7 15:13:13 2005 -0700
Initial revision of "git", the information manager
from hell

14. Git internals

15. 15
Git repository
local repository consists of
three “trees” maintained by git
Working
Directory
Staging Area
.git directory
(Repository)

16. 16
Git repository
remote repositories don’t have
a working directory
Staging Area
.git directory
(Repository)

17. 17
Git repository
actual files – single checkout
of one version of the project
Working
Directory

18. 18
Git repository
a file that stores the information
what will go into the next commit
Staging Area

19. 19
Git repository
a.k.a. the INDEX
Staging Area

20. 20
Git repository
metadata and object database
are stored in the directory
.git directory
(Repository)

21. 21
Basic Git workflow
git init
Working
Directory
Staging Area
.git directory
(Repository)

22. 22
Working
Directory
Staging Area
.git directory
(Repository)
checkout the project
Basic Git workflow
git clone

23. 23
Working
Directory
Staging Area
.git directory
(Repository)
stage fixes
Basic Git workflow
git add

24. 24
Working
Directory
Staging Area
.git directory
(Repository)
commit
Basic Git workflow
git commit

25. 25
Working
Directory
Staging Area
.git directory
(Repository)
Commit
Checkout the project
Stage Fixes
Basic Git workflow

26. 26
Git demo
fresh initialized git repo
Live Demo

27. 27
Git demo
fresh initialized git repo

28. 28
Git demo
stage a file

29. 29
Git demo
modify a stage a file

30. 30
Git demo
commit modified file

31. 31
Unmodified Modified Staged
Stage the file
Commit
Lifecycle of a file in Git
Untracked
Edit the file
Add the file
Remove the file

32. Working

33. 33
Classical VCS
Storing data as changes to a base
version of each file
Version 1
File A ∆1
Checkins over time
Version 2 Version 3 Version 4 Version 5
∆2
∆1 ∆2File B
File C ∆1 ∆2 ∆2

34. 34
Git‘s way
Storing data as a snapshots of the
project over time.
Version 1
File A A1
Checkins over time
Version 2 Version 3 Version 4 Version 5
A2
B1 B2File B
File C C1 C2 C3
A2A1
B B
C2

35. 35
Git‘s way
If a file did not change only a link
to the file is stored
Version 1
File A A1
Checkins over time
Version 2 Version 3 Version 4 Version 5
A2
B1 B2File B
File C C1 C2 C3
A2A1
B B
C2

36. 36
• Everything in Git is check-summed before it is stored
• Checksum used for reference Integrity!
• All objects are stored compressed in the Git Object Database and
referenced by the SHA-1 value of its contents (plus a small header)
SHA-1 References
commit e83c5163316f89bfbde7d9ab23ca2e25604af29
Author: Linus Torvalds <torvalds@ppc970.osdl.org>
Date: Thu Apr 7 15:13:13 2005 -0700
Initial revision of "git", the information manager
from hell

37. 37
• Everything in Git is check-summed before it is stored
• Checksum used for reference Integrity!
• All objects are stored compressed in the Git Object Database and
referenced by the SHA-1 value of its contents (plus a small header)
• SHA-1 hash: 40-character hexadecimal string:
24b9da6552252987aa493b52f8696cd6d3b00373
SHA-1 References

38. 38
Git

39. 39
git add README hello.abap LICENSE
git commit -m “Initial commit”
Git commit
• One commit with pointer to the tree and
the commit metadata
• One tree: commited content & which files
are stored in which blob
• Three blobs for the content of each file

40. 40
a commit and its tree
commit
tree: 92ec2
author: Hendrik
commiter: Hendrik
«Initial commit»
tree
blob: 5b1d3 README
blob: 911e7 hello.abap
blob: cba0a LICENSE
blob
Hello Munich! This is
a README file for the
project….
blob
REPORT ‘Hello’.
WRITE ‘Hello sitMUC’.
blob
BPL Agreement
Beer Public License..
911e7
5b1d3
cba0a
92ec298ca9
Git commit

41. 41
Git commit
commits and parents
911e7
5b1d3
cba0a
92ec298ca9
commit
tree: 92ec2
parent:
author: Hendrik
commiter: Hendrik
Initial commit
Snapshot A
commit
tree: 184ca
parent: 98ca9
author: Hendrik
commiter: Hendrik
Bug fix #4711
Snapshot B
commit
tree: 0de24
parent: 34ac2
author: Hendrik
commiter: Hendrik
Feature request #007
Snapshot C
98ca9 34ac2 f30ab

42. 42
Concept of branches

43. 43
Git branch
a branch and its commit history
911e7
5b1d3
cba0a
92ec298ca9
98ca9
Snapchot A
34ac2
Snapchot B
f30ab
Snapchot C
v1.0 master
HEAD
Tag
Pointer to a specific commit

44. 44
Git branch
git branch testing
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testing
master
master branch
created by git init

45. 45
Git branch
HEAD points to working branch
911e7
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testing
master
HEAD

46. 46
Git branch
git checkout testing
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testing
master
HEAD

47. 47
Git branch
git commit –a –m ‘made a change’
911e7
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cba0a
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testing
master
HEAD
87ab2

48. 48
Git branch
git checkout master
911e7
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cba0a
98ca9 34ac2 f30ab
testing
master
87ab2
HEAD

49. 49
Git branch
git checkout master
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testing
master
87ab2
HEAD
Switching branches
changes files in your
working directory!

50. 50
Git branch
911e7
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C0 C1 C2
testing
master
C3
HEAD
Human Readble keys

51. 51
Git branch
commit on master  new branch
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cba0a
C0 C1 C2
testing
master
C3
HEAD
C4

52. 52
Git branche
git checkout –b hotfix
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cba0a
C0 C1 C2
testing
master
C3
C4 C5
hotfix

53. 53
Git merge
git checkout master
git merge hotfix
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cba0a
C0 C1 C2
testing
master
C3
C4 C5
hotfix

54. 54
Git merge
git branch –d hotfix
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C0 C1 C2
testing
C3
C4 C5
master

55. 55
Got merge
git checkout master
git merge testing
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C0 C1 C2
testing
C3
C4 C5
master

56. 56
Git merge
Three snapshots used in a typical merge
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C0 C1 C2
testing
C3
C4 C5
master
Common
Ancestor Snapshot to
Merge Into
Snapshot to
Merg In

57. 57
Git merge
A merge commit
911e7
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C0 C1 C2
testing
C3
C4 C5
master
C6

58. 58
Git commit consists of 2 things:
1. pointer to the state of your code at some
moment in time
2. zero or more pointers to „parent“ commits
 a Git commit is a node in a graph.
Git repo is one giant graph

59. 59
• Everything in Git is check-summed before it is stored
• Checksum used for reference Integrity!
• All objects are stored compressed in the Git Object Database and
referenced by the SHA-1 value of its contents (plus a small header)
• SHA-1 hash: 40-character hexadecimal string:
24b9da6552252987aa493b52f8696cd6d3b00373
Creating a branch is nothing more than just
writing 40 characters to a file
SHA-1 References

60. 60
development process
use branches for development
and merge them back to the
master branch upon completion

61. 61
local / remote workflow
Quelle: https://www.git-tower.com/learn/git/ebook/en/command-line/remote-repositories/introduction

62. Git in the world of SAP

63. 63
SAP HCP

64. 64
SAP HCP

65. 65
SAP WebIDE

66. 66
SAP WebIDE

67. 67
 Services  Git Services  Best Practices
HCP Git docu

68. 68
SAP at Github

69. ABAP and Git

70. 70
ABAP and Git
http://www.abapgit.org
https://github.com/larshp

71. 71
abapGit
Live Demo

72. 72
More food for thought:
https://git-scm.com/
https://progit.org/

73. Thanks
Hendrik Neumann
h.neumann@reply.de

74. Backup

75. git commands

76. 76
git init
create a new repository
create a new git repository

77. 77
master
create a new repository
“master” is the default name for a
starting branch after git init

78. 78
git clone /path/to/repository
checkout a repository
create a working copy of a
local repository

79. 79
git clone username@host:/path/to/repository
checkout a repository
for a remote repository

80. 80
origin/master
create a new repository
“origin” is the default name Git
gives to the server you cloned from

81. 81
git add <filename>
add & commit
propose changes – add to the
Index

82. 82
git commit -m "msg"
add & commit
commits file to the HEAD – not
yet to the remote repo

83. 83
git push origin master
pushing changes
send changes from local HEAD
to your remote repository

84. 84
git push origin master
pushing changes
change master to whatever
branch you want to push your
changes to

85. 85
git remote add origin <server>
pushing changes
connect local repository to a
remote server

86. 86
branching
branches are used to develop
features isolated from each other

87. 87
branching
the master branch is the
"default" branch

88. 88
branching
use branches for development
and merge them back to the
master branch upon completion

89. 89
git checkout -b feature_x
branching
create a new branch named
"feature_x" and switch to it

90. 90
git checkout -b master
branching
switch back to master

91. 91
git checkout –d feature_x
branching
delete branch "feature_x"

92. 92
git push origin <branch>
branching
push the branch to your remote
repository – make it available for
others

93. 93
update & merge
use branches for development
and merge them back to the
master branch upon completion

94. 94
git fetch origin
update & merge
fetches any new work that has
been pushed to server (no merge!)

95. 95
git pull
update & merge
update local repository to the
newest commit – fetch and merge
changes

96. 96
git merge <branch>
update & merge
merge another branch into your
active branch (e.g. master) and
create a new commit (if there are
no conflicts)

97. 97
git add <filename>
update & merge
resolve merge conflicts on file level
and add / commit it again

98. 98
git diff <source_branch> <target_branch>
update & merge
show differences between
branches / create patches

99. 99
update & merge
use branches for development
and merge them back to the
master branch upon completion

100. 100
git tag
tagging
lists tags in alphabetical order

101. 101
git tag 1.0.0 1b2e1d63ff
tagging
create new “1.0.0” tag for a
commit – referenced by its id

102. 102
git log
log
repo history – parameters can
change the log output

103. 103
git log --author=bob
log
see only the commits of a certain
author, e.g. Bob

104. 104
git log --pretty=oneline
log
compressed log where each
commit is one line

105. 105
git log --graph --oneline --decorate –all
log
ASCII art tree of all the branches,
decorated with the names of tags
and branches

106. 106
git checkout --<filename>
replace local changes
replace local changes in working
tree with last content in HEAD

107. 107
git fetch origin
update & merge
fetches any new work that has
been pushed to server (no merge!)

108. 108
git fetch origin
git reset --hard origin/master
replace local changes
drop all your local changes and
commits, fetch the latest history
from the server and point local
master branch at it

110. 110
checksums in the .git directory

111. 111
git log

112. 112
the .git directory

113. 113
Working
Directory
Index
(Staging Area)
HEAD
(.git directory)
commit
checkout the project
stage fixes
pushing changes
send changes to remote repo
Remote
Repository
push

114. 114
Working
Directory
Staging Area .git directory
commit
pull
stage fixes
pulling changes
get changes from remote repo
Remote
Repository
push