Software Engineering

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1 Software Engineering CSC 331/631 - Spring 2018 Version Control with Git Paul Pauca March 27

2 SE Theory: Version Control Systems Link to video lectures (Soft Dev Proc part 1 of 3) Watch these short videos on your own (54-60) VCS basics, dos and don ts, VCS types (61-64) Git basics

3 Using Git

5 Typical day-to-day use cases Create a local repository $ git init $ git add Add files/directories to the workspace Add changes to the staging area and commit changes to the local repo $ git commit -a -m comment $ git status $ git diff Obtain the status of files in the workspace Compare differences wrt to the local repo Obtain history of changes in the repo $ git log Revert to a previous version $ git reset --hard

6 Git Story 1 Narrative: As owner of an existing code project I want to create a local repo, add, commit, and track changes to files So that I can document and keep better track of my code changes over time

7 Scenario 1.1 Creating a local repository Given I am in my project s directory sampleapp using terminal/command prompt When I type: git init Then a local git repo is created in sampleapp/.git $ cd sampleapp $ git init Initialized empty Git repository in sampleapp/.git/ Your workspace is in sampleapp,.git/ is the local repo You can cd into.git to look but don t change anything!

8 Scenario 1.2 Checking status of files in your project directory Given I am on sampleapp and local repo exists When I type: git status Then I get the current status of files/directories in the workspace We don t want this folder in the $ git status On branch master repo! Initial commit Untracked files: (use "git add <file>..." to include in what will be committed) index.html node_modules/ package.json server.js nothing added to commit but untracked files present (use "git add" to track)

9 Ignoring stuff in the workspace What to ignore Binary files, libraries/modules, Word, Excel, etc. E.g. node_modules How? Create file.gitignore and specify the names of the files or folders to ignore.

10 Scenario 1.3 Adding new files to the workspace Given a directory I want to track using git When I type: git add. Then all files and directories in. will be added to the workspace $ git add. Check the status of your files to confirm If the file is not empty, then it is also added to the staging area

11 Scenario 1.4 Committing files to the local repo Give I have changes in my files When I type: git commit -a -m comment Then the changes files will be added to the staging area and committed to the local repo with the comment I provided $ git commit -m "server implements GET verb [master (root-commit) 28a3ea6] server implements GET verb Committer: Victor Pauca <pauca@victors-macbook-pro.local> 1 file changed, 24 insertions(+) create mode server.js

12 Each commit creates a new tracked version for each file in the local repo.

13 Gotchas! The staging area is emptied once files are committed Files in the workspace must be added first before they are committed to the local repo. Typical failure: forget to add first I modified a file and I commit: git commit -m No version created in the local repo Best to add and commit simultaneously $ git commit a m adding and committing

14 Scenario 1.5 Determining differences wrt to version in local repo Given I made changes to files in the workspace and I want to check those changes relative to the version in the local repo When I type: git diff Then I will get the differences between my files and those in the local repo $ git diff diff --git a/index.html b/index.html index e992c6a..d5d a/index.html ,6 <body> <h1>hello Wake</h1> +<h2>good bye </h2> </body> </html>

15 Scenario 1.6 List history of files in the local repo Given I have committed many files to local repo When I type: git log Then I will get the history of all commits (versions) in the local repo $ git log commit 4481d4163d438eafd718f6e c54db33a25 Author: Paul Pauca <paucavp@wfu.edu> Date: Wed Feb 15 13:29: added 404.html commit 38cd4b0431b5dc75f5125feb9fe58f1877a15848 Author: Paul Pauca <paucavp@wfu.edu> Date: Wed Feb 15 13:29: added login.html commit eea30aec2b496fbdebf236d7a98e8eb4722fd8ba Author: Paul Pauca <paucavp@wfu.edu> Date: Wed Feb 15 11:49: added json file and commited changes to index.html commit 45db3b870fad b23152c51712d755f Author: Paul Pauca <paucavp@wfu.edu> Date: Wed Feb 15 11:36: added html file commit 28a3ea63a98e52bba4eb0f05531f25279aba1b93 Author: Victor Pauca <pauca@victors-macbook- Pro.local> Date: Wed Feb 15 08:42: server implements GET verb

16 Scenario 1.7 Reverting to a previous version Given that I am in my project directory and know the ID of the version I want to revert to When I type: git reset hard ID Then my project directory contents are reset to the contents of version ID in the local repo AND this version is now the latest version $ git reset --hard 38cd4b0431b5dc75f5125feb9fe58f1877a15848 HEAD is now at 38cd4b0 added login.html File 404.html is no longer in the project directory (see previous slide)

17 Working with Branches Branch: separate snapshot of your current code Big Idea: create a branch when working on a new feature Established workflows used in practice, e.g. gitflow Gitflow Workflow:

18 Typical use cases Create a new branch in the local repo $ git branch newbranchname List all the branches in the local repo $ git branch -a Checkout a branch or switch to another branch $ git checkout branchname Tell what branch you are working on $ git branch

19 Git Story 2 Narrative: As a developer I want to use git branches So that features can be independently added to my code without braking the main working branch

20 Scenario 2.1 Creating a branch in the local repo Given I am in my project s directory When I type: git branch <branchname> Then a new branch is created in my local repo from the master branch $ git branch databasefeature List all the branches in the local repo $ git branch -a #list all branches databasefeature * master Workspace shows content of this branch

21 Scenario 2.2 Checking out a branch Given I am in my project s directory When I type: git checkout <branchname> Then my directory switches to the contents of the latest version in branchname $ git checkout databasefeature Switched to branch databasefeature' Now I can code, test and version my database code without affecting the master branch

22 You can add and commit files in this branch as before. Git log only shows the history of this branch.

23 Scenario 2.3 Switching branches Given that I am on a git branch When I type: git checkout <otherbranch> Then my directory switches to the contents of the latest version in otherbranch $ git checkout databasefeature Switched to branch databasefeature' $ ls index.html movies.html package.json login.html node_modules/ server.js $ git checkout master Switched to branch 'master' $ ls index.html login.html node_modules/ package.json server.js

24 Credit: Working with a Remote Repository Allows collaboration by a team

25 Typical use cases Add a remote repository $ git remote add origin URL Push changes to the remote repository $ git push -u origin master Fetch changes from the remote repository $ git fetch Merge my changes locally with the version in the the remote repository $ git merge Pull changes to my work space from the remote repo $ git pull Resolving merge conflicts

26 Git Story 3 Narrative: As a developer working in a team I want to use a remote repository So that I can share my working code with others in the team and update my code with what others developed

27 Scenario 3.1 Adding a remote repository Given that I know the URL to my new repository in Github And I am in the directory for my local master branch When I type: git remote add origin <URL> Then the remote repo in URL is recorded as origin in my computer $ git remote add origin Pushing changes to the remote repository Given that I want to push my local repo to the remote repo When I type: git push -u origin master Then my local repository is pushed to origin $ git push -u origin master

28 Scenario 3.2 Pushing local changes to remote repo Given I have remote changes committed locally And I am in the master branch When I type: git push Then my Github repo is updated with my changes $ git push # or $ git push origin master Caution: push fails if the local repo is behind the remote repo

29 Scenario 3.3 Fetching changes from the remote repo Given that I want to update my local repo with respect to latest commits in the remote repo When I type: git fetch Then my local repo is updated but my workspace is not changed. $ git fetch

30 Scenario 3.4 Merging my workspace with the latest commit in the local repo Given that I fetched the latest changes from the remote repo When I type: git merge Then my workspace is updated with changes brought from the remote repo $ git merge Recall: git pull is the same thing as git fetch followed by git merge

31 Resolving Merge Conflicts Using the command line Using a merge tool f19ff75c60f18b4b8149 Other Moving the local repo back to pre-merge state git reset --hard HEAD^

32 Tagging A tag is a version in the repository with specific historical importance E.g. v0.1, v0.2, v1.0, etc.

33 Git Story 4 Narrative As a developer I would like to create tagged releases and upload them to my remote repository So that releases can be properly document and shared

34 Scenario 4.1 Creating an annotated tag Given I have working version in my local repo When I type: git tag -a VER -m comment Then a version is committed with tag name VER $ git tag -a v0.1 -m first version deployed to Heroku

35 Scenario 4.2 Creating a lightweight tag Given I have working version in my local repo When I type: git tag VER Then a file with a checksum of is saved for VER $ git tag v0.1-lightweight

36 Obtaining info on my tags Given I have a tag saved as VER When I type: git show VER Then I get information about this tag $ git showtag v0.1 tag v0.1 Tagger: Paul Pauca <pauca@barza.cs.wfu.edu> Date: Tue Mar 27 13:41: first version deployed to Heroku Scenario 4.3 commit 3eb602806fa83d f7fe36e09cc88729b9f (HEAD -> master, tag: v0.1, origin/master) Author: Paul Pauca <pauca@barza.cs.wfu.edu> Date: Mon Mar 26 14:45: adding a readme file diff --git a/readme b/readme new file mode index aa26bfd --- /dev/null ,0 +# Sample app for Software Engineering 331/631 Tagger: Paul Pauca <pauca@barza.cs.wfu.edu> Date: Tue Mar 27 13:41: first version deployed to Heroku commit 3eb602806fa83d f7fe36e09cc88729b9f (HEAD -> master, tag: v0.1, origin/master) Author: Paul Pauca <pauca@barza.cs.wfu.edu> Date: Mon Mar 26 14:45: adding a readme file diff --git a/readme b/readme new file mode index aa26bfd --- /dev/null ,0 +# Sample app for Software Engineering 331/631

37 Scenario 4.4 Sharing a tag Given I have a tagged version in my computer When I type: git push origin VER Then tag VER is sent to the remote repository $ git push origin v0.1

FAQ Q: Where/in which branch do I create new code/modify existing code? A: Q: How do I commit new changes? A:

FAQ Q: Where/in which branch do I create new code/modify existing code? A: We strongly recommend only modifying the source code within the local master branch: Git Repository View Woped repository Branches