Post on 21-Jun-2020
Andrei Chis
Distributed version control with git — a brief introduction
based on slides by Oscar Nierstrasz
Why version control?
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Bob
Why version control?
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Bob Carol
Why version control?
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Bob Carol
TedAlice
Why version control?
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Bob Carol
TedAlice
Why version control?
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Bob Carol
TedAlice
Why version control?
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Bob Carol
TedAlice
A recipe for disaster!
Why version control?
�9
Cope with the confusion that happens when multiple people edit
the same files
Why version control?
Bob
Repository
Carol
Bob
Repository
Carol
Bob
Repository
Snapshot Version 1
Carol
Bob
Repository
Version 1
Carol
Bob
Repository
Snapshot
Version 1
Version 2Carol
Bob
Repository
Version 1
CarolVersion 2
Bob
Repository
Version 1
CarolVersion 2
Bob
Repository
Version 1
CarolVersion 2
SnapshotVersion 3
Bob
Repository
Version 1
CarolVersion 2
Version 3
Version 4
Version 5
Version 6
Version 1
Version 2
Version 3
Version 1
Version 2
Version 3
Version 1
Version 2
Version 3
Version 100
Version 101
Version 103
AliceTed
Bob
Repository
Version 1
CarolVersion 2
Version 3
Version 4
Version 5
Version 6
Version 1
Version 2
Version 3
Version 1
Version 2
Version 3
Version 1
Version 2
Version 3
Version 100
Version 101
Version 103
AliceTed
Can still lead to disaster!
Controlled evolution
git
gitTracks the history of a collection of files
gitTracks the history of a collection of files
Can revert the collection of files to another version
git
distributed version control
system
What is acentralized version
control system?
Bob Carol
Central repository
Bob Carol
Central repository
checkout
Bob Carol
Central repository
checkoutcheckout
Bob Carol
Central repository
Bob Carol
Central repository
commit
Bob Carol
Central repository
updatecommit
Bob Carol
Central repository
commit
Bob Carol
Central repository
commit
Bob Carol
Central repository
commit commitconflict
X
Bob Carol
Central repository
commit commitconflict
X
you must update before every commit
What is adistributed version
control system?
Bob Carol
Remote repository(groupXY)
Bob Carol
Remote repository(groupXY)
local repository
clone
Bob Carol
Remote repository(groupXY)
local repository
clone
local repository
clone
Bob Carol
Remote repository(groupXY)
local repository
local repository
Bob Carol
Remote repository(groupXY)
local repository
local repositorycommit
Bob Carol
Remote repository(groupXY)
local repository
local repositorycommit
push
Bob Carol
Remote repository(groupXY)
local repository
local repositorycommit
push pull
Bob Carol
Remote repository(groupXY)
local repository
local repositorycommit
push
Bob Carol
Remote repository(groupXY)
local repository
local repositorycommit
push
Bob Carol
Remote repository(groupXY)
local repository
local repositorycommit
pushcommit
Bob Carol
Remote repository(groupXY)
local repository
local repositorycommit
pushcommitpush
conflict
X
Bob Carol
Remote repository(groupXY)
local repository
local repositorycommit
pushcommitpush
conflict
X
you must pull before every push
groupX
groupX
Remote repository
(p2exercises)
groupX
Remote repository
(p2exercises)
groupX
git remote add p2exercises ...
Remote repository
(p2exercises)
groupX
git remote add p2exercises ...
git pull p2exercises master
Remote repository
(p2exercises)
groupX
Remote repository
(p2exercises)
groupX
do not commit after the deadline; it leads to merge conflicts
Remote repository
(p2exercises)
Basic git
commit
A “commit” is “a set of changes” to a “set of files”
commitcommit
Most commits modify (or merge) earlier commits
commit
branch
commit
A graph of commits may belong to a
branch
commit
master
commit
master is the main branch
commit
HEAD
master
commit
“HEAD “is the current branch
mkdir repocd repogit init
Create a git repo
C0
HEAD
master
git add …
Tell git to “stage” changes
C0
HEAD
master
C1
HEAD
master
git commit …
Commit your changes
C0
Collaborating
Public repoLocal repo
John Jane
Local repo
master
C1
C0
Public repoLocal repo
John Jane
Local repo
git clone …
git clone …
mastermastermaster
C1
C0
C1
C0
C1
C0
Public repoLocal repo
John Jane
Local repo
git add …git commit …
git add …git commit …
mastermastermaster
C0
C1
C0
C1
C1
C0
C2 C3
Public repoLocal repo
John Jane
Local repo
git pull
(nothing new to pull)
mastermastermaster
C0
C2 C3
C1
C0
C1
C1
C0
Public repoLocal repo
John Jane
Local repo
git push
mastermastermaster
C0
C2
C1
C0
C3
C1
C0
C2
C1
Public repoLocal repo
John Jane
Local repo
git pull
master
C1
C0
mastermaster
C0
C2 C2
C1
C0
C1
C3 C2
Public repoLocal repo
John Jane
Local repo
git pull
NB: git pull = fetch + merge
master
C1
C0
mastermaster
C0
C2 C2
C1
C0
C1
C4
C2C3
Public repoLocal repo
John Jane
Local repo
git push
C3
master
C1
C0
C2
master
C1
C0
C2
master
C0
C2
C3C1
C4C4
Public repoLocal repo
John Jane
Local repo
git pull
C3
master
C1
C0
C2C3
master
C1
C0
C2C3
master
C1
C0
C2
C4 C4C4
to be continued
Resources
http://book.git-scm.com/index.htmlhttp://git-scm.com/
https://github.com/
http://www.slideshare.net/chacon/getting-git http://oreilly.com/
http://creativecommons.org/licenses/by-sa/3.0/
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