Oscar Nierstrasz

Distributed version control with git — a brief introduction

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Why git?

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Bob

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Bob Carol

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Bob Carol

TedAlice

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Bob Carol

TedAlice

A recipe for disaster!Thursday, September 15, 11

The git object model

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blob

A “blob” is content under version control (a file)

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You can have trees of blobs(directories of files)

blobblob

tree

treeblob

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A “commit” is a tree of blobs(a set of changes)

blob

commit

blob

tree

treeblob

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Most commits modify (or merge) earlier

commitscommit

blob

tree

blob

commit

blob

tree

treeblob

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You can “tag” an interesting commit

commit

blob

tree

tag

blob

commit

blob

tree

treeblob

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A graph of commits may belong to a branch

commit

blob

tree

tag

branch

blob

commit

blob

tree

treeblob

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commit

blob

tree

tag

HEAD

branch

blob

commit

blob

tree

treeblob

“HEAD “is the current branch

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Let’s focus on commits and branches

commit

HEAD

branch

commit

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Basic git

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mkdir repocd repogit init

Create a git repo

C0

HEAD

master

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git add …

Tell git to “stage” changes

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HEAD

master

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C1

HEAD

master

git commit …

Commit your changes

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Collaborating

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Public repoLocal repo

John Jane

Local repo

master

C1

C0

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Public repoLocal repo

John Jane

Local repo

git clone …

git clone …

mastermastermaster

C1

C0

C1

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Public repoLocal repo

John Jane

Local repo

git add …git commit …

git add …git commit …

mastermastermaster

C0

C1

C0

C1

C1

C0

C2 C3

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Public repoLocal repo

John Jane

Local repo

git pull

(nothing new to pull)

mastermastermaster

C0

C2 C3

C1

C0

C1

C1

C0

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Public repoLocal repo

John Jane

Local repo

git push

mastermastermaster

C0

C2

C1

C0

C3

C1

C0

C2

C1

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Public repoLocal repo

John Jane

Local repo

git fetch

mastermastermaster

C0

C2 C2

C1

C0

C3

C1

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C2

C1

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Public repoLocal repo

John Jane

Local repo

git merge

NB: git pull = fetch + merge

C3

master

C1

C0

C2

mastermaster

C0

C2 C2

C1

C0

C1

C4

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Public repoLocal repo

John Jane

Local repo

git push

C3

master

C1

C0

C2

master

C1

C0

C2

master

C0

C2

C3C1

C4C4

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Public repoLocal repo

John Jane

Local repo

git pull

C3

master

C1

C0

C2C3

master

C1

C0

C2C3

master

C1

C0

C2

C4 C4C4

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Branching and merging

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“origin” refers to the remote repo

C1

master

C0

origin/master

HEAD

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…git commit …

C1

master

C0

origin/master

HEAD

C2

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git branch tryout

C1

master

C0

C2

tryout

origin/master

HEAD

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git checkout tryout

NB: git checkout –b … = branch + checkout

C1

master

C0

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tryout

origin/master

HEAD

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git commit …

C1

master

C0

C2

tryout

origin/master

HEAD

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git fetch origin

C1

master

C0

C2

tryout

C3

origin/idea

origin/master

HEAD

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C6

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git merge origin/master origin/idea

C1

master

C0

C2

tryout

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origin/idea

origin/master

HEAD

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git checkout master

C1

master

C0

C2

tryoutHEAD

C3

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C5

C6

origin/idea

C7

origin/master

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git merge

C1

master

C0

C2

tryoutHEAD

C3

C4

C5

C6

origin/idea

C7

origin/master

C8

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C1

master

origin/master

C0

C2

tryout

git push

HEAD

C3

C4

C5

C6

origin/idea

C8C7

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More to git

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More to git …

> Merging and mergetool> Squashing commits when merging> Resolving conflicts> User authentication with ssh> gitx and other graphical tools> git configure — remembering your name> git remote — multiple remote repos> github — an open source public repo> …

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Resources

http://book.git-scm.com/index.htmlhttp://git-scm.com/

https://github.com/

http://www.slideshare.net/chacon/getting-git http://oreilly.com/

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