So#ware(Project Lecture'3 Wouter'Swierstra - - PowerPoint PPT Presentation

So#ware(Project

Lecture'3 Wouter'Swierstra

So#ware(project(–(Lecture(3 1

Last%&me

• Scrum'planning
• Product'backlog

So#ware(project(–(Lecture(3 2

Working(effec,vely(with(git(and(GitHub.

So#ware(project(–(Lecture(3 3

Collabora've*so,ware*development

You$have$two$weeks$to$finish$your$user$stories. And$need$to$give$a$demo$at$the$end.

How$can$you$develop$different$stories$in$parallel$without$ breaking$your$working$prototype?

So#ware(project(–(Lecture(3 4

Version(control

So#ware(project(–(Lecture(3 5

What%is%git?

• A#popular,#powerful#distributed#file#version#control#system
• It#is#free#and#obtainable#from#git;scm.com
• Originally#developed#to#manage#the#Linux#kernel
• An#esBmated#27#percent#of#professional#developers#uses#Git#

(May#'12).

So#ware(project(–(Lecture(3 6

Ge#ng&to&grips&with&git

• Git%is%a%very%powerful%tool%with%many%different%features.
• The%user%interface%takes%some%ge<ng%used%to...
• When%used%correctly,%it%can%be%extremely%effecAve.
• If%you%screw%up,%there%is%usually%a%way%to%undo%your%changes.

So#ware(project(–(Lecture(3 7

Star%ng(a(new(repo

$ git init Initialized empty Git repository in .git/

Add#the#README.md#file#to#the#repository

$ git add README.md

Commit&the&changes&you&made&to&README.md

$ git commit -m "Added README.md"

So#ware(project(–(Lecture(3 8

Cloning'an'exis,ng'repository

To#get#your#hands#on#a#copy#of#an#exis4ng#repository#use:

$ git clone git://github.com/wouter-swierstra/SoftwareProject

Note%that%git clone%supports%several%different%protocols,% including%SSH.

So#ware(project(–(Lecture(3 9

Git$vs$Svn

Git$is$a$distributed$version$control$system:

• a#copy#of#a#repository#can#share#changes#with#any#other#copy.
• almost#all#commands#operate#on#your#local%copy
• sharing#changes#with#others#happens#in#two#steps:
• commi8ng#your#changes#locally
• pushing#these#changes#to#a#remote#server

So#ware(project(–(Lecture(3 10

Git$terminology

Picture(from(Sco-(Chacon's(Pro$Git.

So#ware(project(–(Lecture(3 11

Git$status

$ git status # On branch master nothing to commit (working directory clean) $ emacs 04-slides.md $ git status # On branch master # Untracked files: # (use "git add <file>..." to include in what will be committed) # # 04-slides.md

So#ware(project(–(Lecture(3 12

Adding&new&files

$ git add 04-slides.md $ git status # On branch master # Changes to be committed: # (use "git reset HEAD <file>..." to unstage) # # new file: 04-slides.md

So#ware(project(–(Lecture(3 13

Staging'modified'files

Similarly,)we)can)stage)modified)files)using)git add.

$ emacs README.md $ git add README.md # On branch master # Changes to be committed: # (use "git reset HEAD <file>..." to unstage) # # new file: 04-slides.md # modified: README.md

Git$gives$you$control$over$which$files$to$include$in$a$single$commit.

So#ware(project(–(Lecture(3 14

Pro$%p:(.gi%gnore(to(minimize(noise

Generated(binaries,(documenta1on,(and(so(forth(are(not(under( version(control,(but(keep(showing(up(when(you(run(git status. You$can$have$a$.gitignore$file,$lis0ng$the$files,$directories,$and$ pa6erns$that$you$want$git$to$ignore:

$ cat .gitignore *.pdf .DS_Store build/

So#ware(project(–(Lecture(3 15

Commi%ng(your(changes

The$git commit$command$commits$all$the$staged$changes.

$ git commit -m "Added 04-slides.md; updated README.md" [master 76d15ab] Added 04-slides.md; updated README.md 1 files changed, 1 insertions(+), 0 deletions(-) create mode 100644 04-slides.md

These%changes%are%recorded%locally%but%not%yet%shared%with%others.

So#ware(project(–(Lecture(3 16

Not$men(oned

• git mv"to"rename"files,"without"losing"their"history
• git rm"to"remove"files"from"the"repository
• git commit -a"to"record"all"your"changes"to"tracked"files
• git log"to"get"an"overview"of"recent"changes
• git reset"to"undo"changes

So#ware(project(–(Lecture(3 17

Sharing(your(changes

All#these#commands#operate#on#your#local#copy#of#the#repository. Nothing(is(shared(with(others(yet.

• git pull"–"pulls"in"changes"from"some"other"repository
• git push"–"pushes"your"changes"to"another"repository

These%commands%communicate%with%remote&repositories.

So#ware(project(–(Lecture(3 18

Basic&usage:&git&push

$ git clone git://github.com/wouter-swierstra/SoftwareProject ... $ emacs 04-slides.md $ git commit -am "Updated slides on git" $ git push

So#ware(project(–(Lecture(3 19

Showing(remote(repositories

$ git clone git://github.com/wouter-swierstra/SoftwareProject ... $ git remote -v

• rigin git://github.com/wouter-swierstra/SoftwareProject (push)
• rigin git://github.com/wouter-swierstra/SoftwareProject (fetch)

So#ware(project(–(Lecture(3 20

Pull$changes$from$remote$repositories

$ git pull remote: Counting objects: 45, done. remote: Total 45 (delta 2), reused 2 (delta 2), pack-reused 43 Unpacking objects: 100% (45/45), done. From https://git.science.uu.nl/swier004/my-repository 543d40c..8497463 master -> origin/master * [new branch] redirect -> origin/redirect Updating 543d40c..8497463 Fast-forward ...

So#ware(project(–(Lecture(3 21

The$real$challenge

This%covers%the%very%basic%git%opera0ons. You$can$now$collaborate$on$a$single$codebase. But$collabora+ng$effec$vely$is$not$easy.

So#ware(project(–(Lecture(3 22

GitLab

The$university$provides$a$repository$hos1ng$service,$GitLab:

• Repository
• Issue-tracker
• Wiki
• Useful-graphical-interface

Many%complex,%yet%common,%opera0ons%can%be%done%through%the% GitLab%GUI.

So#ware(project(–(Lecture(3 23

Gitlab

So#ware(project(–(Lecture(3 24

Branching

Git$makes$it$very%easy$to$work$on$different$versions$of$your$ so4ware. Use$branches$to$isolate$different$all$the$stories$being$developed$in$ an$itera4on. Create&one&branch&per&story&at&the&beginning&of&the&itera2on. Merge%each%branch%back%to%master%at%the%end%of%the%itera3on.

So#ware(project(–(Lecture(3 25

Golden'rules

• 1. The&master&branch&may&only&contain&code&that&is&tested,&

reviewed&and&ready&to&be&released.

• 2. Only&commit&code&that&compiles,&even&in&experimental&branches.
• 3. No&branch&lives&more&than&three&itera=ons

(the&master&branch&excluded).

• 4. Create&pull&requests&for&every&new&branch.&Only&merge&your&

changes&if&everyone&is&happy.

So#ware(project(–(Lecture(3 26

So#ware(project(–(Lecture(3 27

Working(with(merge(requests

Create&branch&with&your&feature&new&feature git checkout -b new_feature ... git commit -am "My feature is ready" git push origin new_feature Create&a&merge&request&from&this&commit. Members'of'your'team'can'review'the'code'&'merge'it'with'main.

So#ware(project(–(Lecture(3 28

Merge%requests%demo

So#ware(project(–(Lecture(3 29

Working(with(merge(requests

One$or$two$people$responsible$for$merging$branches$with$main. Before&a&branch&is&merged&with&the&main&branch,&there&should&be&a& code&review. Use$the$forum$for$discussion$if$there$are$issues$with$the implementa4on,$execu4on,$tests,$etc.

So#ware(project(–(Lecture(3 30

Code%reviews

• Does&the&code&work?
• Is&it&easy&to&understand&and&clearly&structured?
• Does&it&adhere&to&coding&conven8ons?
• Are&there&comments?
• Are&there&any&open&TODOs&or&obviously&unfinished&methods?
• Is&there&an&automated&test&for&this&feature/bug?

So#ware(project(–(Lecture(3 31

Code%reviews

If#the#answer#to#any#of#these#ques0ons#is#no#–#don't#merge. Merging'with'master'exposes'your'work'to'the'rest'of'the'team. Breaking)their)work)means)was0ng)everybody's)0me. Inves&ng(in(quality(assurance(now(will(be(invaluable(later.

So#ware(project(–(Lecture(3 32

Wri$ng'good'comments

• Don't'explain'obvious'details,'instead'focus'on'the'key'ideas.
• Bad:'\\This for loop iterates over the array
• Be<er:'\\This method computes the sum of a non-

empty array storing positive integers

• Document'invariants,'assump?ons,'unusual'behaviour'and'

corner'cases.

• Explain'the'design'decisions'you'made'that'lead'to'this'code.

So#ware(project(–(Lecture(3 33

Wri$ng'good'comments

• The%goal%is%not%to%explain%the%micro3details%on%every%line%of%

code...

• ...%but%rather%to%help%a%new%reader%understand%the%big%picture%of%

what%is%going%on.

So#ware(project(–(Lecture(3 34

Further'reading

• Lessons'in'so)ware'development
• Pro4git
• A'tutorial'on'merge'requests'and'issues'in'Gitlab
• GitLab'introduc<on'videos'on'Youtube
• Lessons'learned'in'so)ware'development

So#ware(project(–(Lecture(3 35

So#ware(project(–(Lecture(3 36