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First: Recap/2012

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• Distributed Version control

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DistributedV rsi n C ntr l

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Version ControlAll developers have their own local repository

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1. Developers work on their working copy

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2. Developers commit changes of the working copy to their own local repository first

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3. Changes can be exchanged between repositories (“pushed” and “pulled”)

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LocalRepository

NetworkWorkingCopyA

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LocalWorkingC “Central”B

The

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RepositoryB

Push and Pull/2012

Push• Once developers have committed versions on their

l l it th h th t th

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• Versions are pushed from local branches into corresponding remote branches

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p g• Like “commit” from one repo to anotherPull

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• Latest versions are pulled from remote branchesand put into the corresponding local branches

• Like “update” from one repo to another

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LocalRepository

NetworkWorkingCopyA

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Working “C t l”

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gCopy “Central”

RepositoryB

DistributedV rsi n C ntr l

/2012

Version Control• Local and remote repositories are technologically

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• Chaining of repositories is possible.

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• Several personal repositories can be used:• Good for testing of new commits:

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• one repo for development, one for staging

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LocalRepository

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LocalWorkingC “Central”

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Repository

Mercurial/2012 • Open-source project, started around 2005

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j• Used for many open-source projects

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• Every developer has a repository, which is a folder• Repo folder contains working copy,

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p g py,and a subfolder .hg which contains the version data

• Versions are identified locally by natural numbers

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and globally by hash values,e.g. 5c240805ac2d9530b780cbd514574af398c0cdd6G d l (T i H )

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Working with Hg/2012

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1. Start by cloning existing repo, or creating new one

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y g g p , g– New repo has only “default branch” (like trunk)– After cloning you have local copies of all branches

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f g y p fof parent repo

2. Modify working copy and commit to create new

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y g pyversions in your local repo

3. Pull to load new versions from parent repo into local

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repo– Does not change working

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put in separate branch

The

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Most important tool: Tortoise xpl r r

/2012

explorer• Integrated

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gcontrol GUIfor mercurial

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to explore thefunctions a bit on your own and figure

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• After all, every GUI is intuitive, right?

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commit/2012 • Creates a new version on

h l l

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• Best practices:

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• Make sure to add new(a.k.a. untracked)files

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be only one logical

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• Never break the build!

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• Never break the tests. 9

Hg Pull/2012

gPull regularly to stay up to date.H itt d l l i

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on some branch?1 If no you can update to the latest

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– Changes in working copy are merged with pulled version

– Unless you choose to

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2. If you have committed local versions

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Lab Setup/2012

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• Create one repo: repo1

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p p• Create one file in the working copy of repo1• Add it to version control, can you figure out how?

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, y f g• Commit it.• Clone the repo: repo2

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Clone the repo repo2

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Lab Task 1/2012

• Change a file in the working copy of repo1

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g g py p• Commit to repo1.• What is on repo2?

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p• Pull on repo 2. What do you see?• Update on repo 2

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Update on repo 2

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Hg Push/2012

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Push regularly to integrate your changes.

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g y g y gHave others committed versions on a remote branch

that you have committed to locally?

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1. If no, push will succeed and the local versions will be in the remote repo

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2. If yes, i.e. others have committed versions on a branch you have

itt d t l ll

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e committed to locally:– You need to merge your versions

with their versions

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remote branches are merged

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Lab Task 2/2012

• Change something in the working copy of repo2.

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g g g py p• Commit to repo2• What is on repo1?

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p• Push in repo 2 to repo1. What do you see?

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Lab Task 3/2012

• Change a file in the working copy of repo1

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g g py p• Commit to repo1.• Change a different file in the working copy of repo2.

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g ff f g py f p• Commit to repo2• Pull on repo 2. What do you see?

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Pull on repo 2. What do you see?• Push in repo 2 to repo1. What happens?

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Lab Task 4/2012

• Reproduce the conflict from Lab task 3:

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p• Use “merge” on repo2, applying it to the two latest

commits. Can you figure out how to do that?

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• Push in repo 2 to repo1. What happens?

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Lab Task 5/2012

• Change a file in the working copy of repo1

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g g py p• Commit to repo1.• Change a different file in the working copy of repo2.

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g ff f g py f p• Pull on repo 2. What do you see?• Update, using “merge local changes”

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Update, using merge local changes• Now commit on repo2.• Push in repo 2 to repo1 What happens?

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task 4?

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Lab Task 6/2012

• Change a file in the working copy of repo1

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g g py p• Commit to repo1.• Change a different file in the working copy of repo2.

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g ff f g py f p• Commit to repo2 under a named branch tryout• Pull on repo 2. What do you see?

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Pull on repo 2. What do you see?• Push in repo 2 to repo1. What happens?• What is the difference to before?

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Lab Task 7/2012

• Reproduce the final situation of Lab Task 6:

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p• Use merge on repo2, on default branch and tryout

branch

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• Push in repo 2 to repo1. What happens?• Compare with Lab Task 4

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Extensions Tab/2012

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Extensions/2012 • Transplant: Moving a commit from one branch to

another

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• Strip: deleting one or several commits on a local repository

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Lab Task E1/2012

• Reproduce the conflict from Lab task 3:

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p• Strip one head. Can you figure out how to do that?• Push in repo 2 to repo1. What happens?

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p p pp• Stripping changes is NOT the standard way to deal

with conflicts, the standard way is merging.

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Lab Task E2/2012

• Reproduce the conflict from Lab task 3:

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p• Transplant one head to the other branch. Can you

figure out how to do that?

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• Strip one head, which one makes sense?• Push in repo 2 to repo1.

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p p• Compare with merging.

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Work routine for committing/2012

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• If you think you are ready to commit

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y y y1. Run tests. If they fail, do not commit2. Pull commits

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mm3. If there are changes, update to the latest commit,

back to 1.

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4. Check all files that need to be committed.5. Commit

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6. Push (this is crucial, commit alone doesnt make it available for others.

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Version ControlBest Practices

/2012

Best Practices1. Complete one change at a time and commit it

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undo/redo them individually– If you don’t commit and your hard disk crashes

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2. Only commit changes that preserve system integrity

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y g p y g y– No “breaking changes” that make compilation or tests fail

3. Commit only source files (e.g. not .class files)

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4. Write a log entry for each change– What has been changed and why

5 Communicate with the other developers

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g g– Follow the project guidelines & specifications