Git tutorial

ioning You r Code:
Vers
Git and Github™:
Code Management and
Sharing for Researchers
using Git
Eliezer Kanal
10/24/2011 and Github
(™)

Slides available online!

!""#$%%"&'()*+,-./%-'0-1&"2

What is Versioning?
• Keeping track of changes to your code
• Documenting those changes
• You’re probably doing it now...

Why Change?

• Troubleshooting
• Logging
• Simplify adding
features

• Simplify code
sharing

What is Git?
• DVCS = Distributed Version Control System
• Technique for managing large/small coding projects

Large

Me, >1 million other
Small
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^ﬁledhistory
e
distribut

What does Git do?
• Branching & Merging

version 1 version 2 version 3 version 4 version 5

version 4b version 4b.2
nch
new feature bra

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
bad word!

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

• Downloaded, found bug
• Fixed bug, multiple local
check-ins

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

How Git can help YOU *

• Personally: • CNBC as a group:
- Keep track of changes - “Don’t reinvent the
wheel”
- Fix bugs quicker
- More eyes → better code
- Share code easier
- Collaboration
- Simplify adding new
features/changing code

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

This slide intentionally left blank

Key Concepts
Things “about History, Same as
Work is
to be stored” branches are Repository,
done here
are put here stored here but remote
781&"8#)5!
781&"8966 781&"8-.//&"
781&"8#)++

Staging
Workspace Repository Remote
Area

• Create & edit some code
/9"!,/
:)'-"&.'8/9"!;<

*3")*'8=>=?

• Move code to Staging Area

• Commit code

• Make changes, start working on new code
/9"!,/
:)'-"&.'8/9"!;< #*&'",/
:)'-"&.'8#*&'";9<
*3")*'8=>=? /9"!,/
3-!.89?
:)'-"&.'8/9"!;9@0<

*3")*'89>0?

…wash, rinse, repeat:

• Move completed code to
“Staging Area”

- Leave the rest “unstaged”

• Commit code

Key Concepts
• Finder (Explorer) not suited for Git
- Are these in the workspace
or staging area?

- What branch are we on?

- What revision is this?

Not enough information!

Git Interface
• Command line
• GUI
- Github for Mac
(signific
antly ) differe
ntly
ightly
All work sl
- GitExtensions

- Others

Example Usage
• Starting work on /(A*.B3-":
Terminal
78-68/(A*.B3-"
781&"8&'&"8

That’s it!

• Code is in working state; ready for “commit”
Terminal
781&"89668/9"!,/
781&"8-.//&"84/8C-*39"368/9"!8:)'-"&.'D

• Make changes, add new code
/9"!,/
:)'-"&.'8/9"!;< #*&'",/
:)'-"&.'8#*&'";9<
*3")*'8=>=? /9"!,/
3-!.89?
:)'-"&.'8/9"!;9@0<

*3")*'89>0?

• See what we’ve done
Terminal
781&"85"9")5
E8F'80*9'-!8/95"3*
E8G!9'1358'."85"91368:.*8-.//&"$
E8;)538H1&"89668I:&+3J,,,H8".8)#69"38K!9"8K&++8038-.//&""36<
E
E8 /.6&:&36$8/9"!,/
E
E8L'"*9-M368:&+35$
E888;)538H1&"89668I:&+3J,,,H8".8&'-+)638&'8K!9"8K&++8038-.//&""36<
E
E8 #*&'",/
'.8-!9'1358966368".8-.//&"8;)538H1&"8966H89'6%.*8H1&"8-.//&"849H<

• Add...
Terminal
781&"89668/9"!,/
781&"89668#*&'",/
781&"85"9")5
E8F'80*9'-!8/95"3*
E8G!9'1358".8038-.//&""36$
E888;)538H1&"8*353"8NOPQ8I:&+3J,,,H8".8)'5"913<
E
E8 /.6&:&36$888/9"!,/
E8 '3K8:&+3$888#*&'",/
E

• …and Commit
Terminal
781&"8-.//&"84/8R966368S9*&90+358".8/9"!@8'3K8#*&'"8:)'-"&.'R
T/95"3*89U3-VW9X8966368S9*&90+358".8/9"!@8'3K8#*&'"8:)'-"&.'
8=8:&+358-!9'136@8=8&'53*"&.'5;><@8W863+3"&.'5;4<
8-*39"38/.638=WWVYY8#*&'",/

• Let’s see what we’ve done...
Terminal
781&"8+.1
-.//&"89U3-VW9ZVU:6VY3=[ZU9WVW=6U[2[03V]U:-U99
P)"!.*$8O+&3^3*8_9'9+8I3M9'9+`-/),36)J
Q9"3$888a!)8b)'8=V8=[$=$2=82W==84WYWW

8888966368S9*&90+358".8/9"!@8'3K8#*&'"8:)'-"&.'

-.//&"8603[]WW]9303V000[30:0-]9=]VY=6]2ZWW
P)"!.*$8O+&3^3*8_9'9+8I3M9'9+`-/),36)J
Q9"3$888a!)8b)'8=V8=[$==$WY82W==84WYWW

8888-*39"368/9"!8:)'-"&.'

Git Workﬂow – Complete
• Do some work
• See what you’ve changed, verify things look good:
re out
781&"85"9")5 Home work: figu
does
781&"86&::"..+8I:&+3'9/35J what this

• Tell Git what you’re ready to commit:
781&"89668I:&+3'9/35J

• Commit & log changes:
781&"8-.//&"8I:&+3'9/35J
!"#$%&'(&%)$*&('*+,'-+%&./

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

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

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

Branches & Merges
• 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
/9')9+,!"/+E*35.+S&'1494/3*13

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

Branches & Merges
• Conflicts: Same code was changed in both branches
• Merge fails!
• Fix by hand, re-try the merge
- !""#$%%KKK,M3*'3+,.*1%#)0%5.:"K9*3%5-/%1&"%6.-5%)53*4
/9')9+,!"/+E*35.+S&'1494/3*13

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

c&"!)0,-./

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.

c&"!)0,-./
• Very easy collaboration
• Clear, detailed setup instructions
4 !""#$%%!3+#,1&"!)0,-./%
• 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 Setup – one-time
Recommend downloading
xcode, just for the
FileMerge program
(“opendiff” when launched
from command line)

• Identify yourself to Git:
781&"8-.':&18441+.09+8)53*,'9/38He.)*8f9/3H88
781&"8-.':&18441+.09+8)53*,3/9&+8H(.)*`3/9&+,-./H8

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

• Give Git some color to make things easier to read:
781&"8-.':&18441+.09+8-.+.*,)&89)".8

• Line-ending bandaids:
781&"8-.':&18441+.09+8-.*3,59:3-*+:8"*)38
781&"8-.':&18441+.09+8-.*3,9)".-*+:8&'#)"
“"*)3”
Windows users: use
“&'#)"”
instead of

Git Setup
• Begin using Git for a project:
78-68#*.B3-"g.+63*%
781&"8&'&"
h'&"&9+&^3683/#"(8c&"8*3#.5&".*(8&'8%#*.B3-"g.+63*%,1&"%

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

• Add files to repository:
781&"89668,
781&"8-.//&"84/8i:&*5"8-.//&"j

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

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