git tutorial

Git and Github™: Code Management and Sharing for Researchers

Eliezer Kanal10/24/2011

Versioning Your Code:

using Gitand Github

(™)

Slides available online!

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What is Versioning?

• Keeping track of changes to your code

• Documenting those changes

• You’re probably doing it now...

Why Change?

• Troubleshooting

• Logging

• Simplify addingfeatures

• Simplify codesharing

What is Git?

• DVCS = Distributed Version Control System

• Technique for managing large/small coding projects

Large

Small Me, >1 million other people

What is Git?

• Two parts:

1. “Database” (hidden folder) to hold project history

2. Set of tools to interact with database

• Used via Command Line or GUI interfaces

What does Git do?

• Retain file history

What does Git do?

• Retain file historydistributed^

What does Git do?

• Branching & Merging

version 2 version 3 version 4

version 4b.2

version 5

version 4b

version 1

new feature branch

Case Study – Analysis toolkit

• Improve interface, ~2 days work

- …while analyzing data

• Branch!

- Improvements on“development” branch

- Work on “main” branch

- Merge when feature completed

Case Study – Productivity tool• 13"45!&"46.'3: productivity

tool, on 1&"!)0,-./

• Downloaded, found bug

• Fixed bug, multiple localcheck-ins

• Sent change historiesback via 1&"!)0,-./

bad word!

How Git can help YOU

• Personally:

- Keep track of changes

- Fix bugs quicker

- Share code easier

- Simplify adding new features/changing code

• CNBC as a group:

- “Don’t reinvent the wheel”

- More eyes → better code

- Collaboration

*

* Or Mercurial, or Bazaar, or Monotone, or LibreSource, or...

This slide intentionally left blank

Git Usage

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Key Concepts

WorkspaceStaging Area Repository

Work is done here

Things “about to be stored” are put here

Remote

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Same as Repository, but remote

History, branches are stored here

• Create & edit some code

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• Move code to Staging Area

• Commit code

• Make changes, start working on new code

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• Move completed code to“Staging Area”

- Leave the rest “unstaged”

• Commit code

…wash, rinse, repeat:

Key Concepts

• Finder (Explorer) not suited for Git

Not enough information!

- Are these in the workspaceor staging area?

- What branch are we on?

- What revision is this?

Git Interface

• Command line

• GUI

- Github for Mac

- GitExtensions

- Others

All work slightly (significantly)

differently

Example Usage

• Starting work on /(A*.B3-":

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That’s it!

Command Line Interface

• Create & edit some code

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• Code is in working state; ready for “commit”

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• Make changes, add new code

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• See what we’ve done

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• Add...

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• …and Commit

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• Let’s see what we’ve done...

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Git Workflow – Complete

• Do some work

• See what you’ve changed, verify things look good:

• Tell Git what you’re ready to commit:

• Commit & log changes:

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781&"86&::"..+8I:&+3'9/35JHomework: figure out

what this does

Github for Mac™

Branches

• Branches let us work in a “new directory” which we can later either delete or merge.

• Question: How can we integrate new features without messing up our current working code?

Branches

• Think of branches as separate folders, each with it’s own content and history.

& Tags

Bran

ches

– G

o N

uts

Branches

• If a branch is a split in the graph, then merge is a merging of split branches

• One single command (SVN users rejoice!)

• Conflicts: Same code was changed in both branches

• Fix by hand, re-try the merge.

- !""#$%%KKK,M3*'3+,.*1%#)0%5.:"K9*3%5-/%1&"%6.-5%)53*4

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- better idea: Google “fixing a git merge conflict”

& Merges

Branches

• Conflicts: Same code was changed in both branches

• Merge fails!

• Fix by hand, re-try the merge

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- better idea: Search “fixing a git merge conflict”

& Merges

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git·hub /'ɡɪtˌhʌb/GitHub is the best way to collaborate with others. Fork, send pull requests and manage all your public and private git repositories.

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• Very easy collaboration

• Clear, detailed setup instructions

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• Easy “forking” for Github projects

- Get your own copy of their code

- Contribute back with “pull requests”

SVN integration

• Very easy to move from SVN → Git

• Works best as one-time deal, can work side-by-side

• !""#$%%.*35"&5,1*%0+.1%2WWU%WU%2\%1&"45S'4")".*&9+%

Good Git Practice

• Check in often!

- Rule of thumb… check in whenever code works

• Write detailed log notes! You’ll thank yourself for it later!

• Branch for new features

- Avoid working on the master branch, it should always be the “clean, working” code

References• Pro Git - free online: ! !""#$%%#*.1&",.*1%0..M%

• Branching:! !""#$%%'S&3,-./%#.5"5%945)--355:)+41&"40*9'-!&'14/.63+%

• Git tutorials and useful FAQ links:! !""#$%%5&d*3S&5&.'5,-./%*35.)*-35%1&"4")".*&9+54031&''3*5%

• Github:! !""#$%%1&"!)0,-./%

• Git-SVN integration:! !""#$%%.*35"&5,1*%0+.1%2WWU%WU%2\%1&"45S'4")".*&9+%

• Google:! !""#$%%1..1+3,-./%

• Bing:! !""#$%%0&'1,-./%

Git Hands-On

Git Setup – one-time

• Identify yourself to Git:

All your work is logged using the name/email you provide here.

• Give Git some color to make things easier to read:

• Line-ending bandaids:

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Recommend downloading xcode, just for the FileMerge program (“opendiff” when launched from command line)

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Windows users: use “"*)3”

instead of “&'#)"”

Git Setup

• Begin using Git for a project:

Creates the (hidden) ,1&" folder. No files being tracked yet.

• Add files to repository:

Instructs Git to manage all files in the folder %#*.B3-"g.+63*%.

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