Git and GitHub Exercises

Getting Started with Git

Exercise 18

1. Start a repository in a new directory.

2. Create a new file in your new Git repository. Make sure Git is tracking the file and then create a new commit.

3. Make changes to the file, and then commit these changes.

4. Add two new files to your repository, but only commit one of them. What is the status of your repository after the commit?

5. Undo the last commit, add the untracked file, and redo the commit.

Solution to

# 1
cd $(mktemp -d)
pwd
git init

# 2
echo hello > README.md
git add README.md
git status README.md
git commit -m initial

# 3
echo sunshy! >> README.md
git commit README.md -m 'add name'

# 4
echo echo Namaste > README.in.md
echo echo Merhaba > README.tr.md
git add README.in.md
git commit -m 'add translations'
git status

# 5
git reset --soft HEAD~
git status  # README.in.md should be in `staged` state
git add README.tr.md
git commit -m 'add translations'
git status

Important Git Features

Exercise 19

1. Look at the help pages for git log and git diff.

2. Add to the .gitignore you already started to include a specific file name, then add that file to your repository.

3. Create a file that contains the Git log for this repository. Use grep to see which day of the week most of the commits occurred on.

Solution to

1. for git log the --oneline option looks nifty:

   cd $(mktemp -d)
   pwd
   git init
   
   for i in {1..5}
   do
       echo $i >> f
       git add f; git commit -m $i
   done
   echo =================
   echo WITHOUT --oneline
   echo =================
   git log
   echo =================
   echo WITH --oneline
   echo =================
   git log --oneline
   

   To see our last log:

   cd $(mktemp -d)
   pwd
   git init
   
   for i in {1..5}
   do
       echo $i >> f
       git add f; git commit -m $i
   done
   
   git log -1
   

   git log is also useful to see the commits between two commits. Every commit is unique and described by a long hash number (e.g., 01fda1b4d72c21760fdffcd5cc4e132570e0001f) but the first digits of this hash number are typically enough for identifying the commit (e.g., 01fda1b). Instead of commits we can use also use the alias HEAD, branch names, or tags (if tags exist in the repository). Let us show the changes between the first and second version:

   cd $(mktemp -d)
   pwd
   git init
   
   echo 1 >> f
   git add f; git commit -m 1; git tag v1
   
   for i in {2..5}
   do
   echo $i >> f
   git add f; git commit -m $i
   done; git tag v2
   
   echo 6 >> f
   git add f; git commit -m 6;
   
   git log --oneline v1..v2
   

   git diff is useful to see your modifications to your last commit:

   cd $(mktemp -d)
   pwd
   git init
   
   for i in {1..5}
   do
       echo $i >> f
       git add f; git commit -m $i
   done
   
   echo 6 >> f
   echo -1 >> g
   git diff
   

   Note that modifications to g are not shown because g is not part of the repo.

2. Git will not accept this and will warn you:

   cd $(mktemp -d)
   pwd
   git init
   echo 1 >> f.txt
   touch g.log
   echo '*.log' > .gitignore
   git add g.log f.txt
   

3. cd $(mktemp -d); pwd
   git clone https://github.com/seankross/the-unix-workbench; cd *
   git log > log
   for day in Mon Tue Wed Thu Fri Sat Sun
   do
       echo $(grep -c $day log) commits on $day
   done | sort --numeric | tac
   

Branching

Exercise 20

1. Start a new branch.

2. Switch to that branch and add commits to it. Switch to an older branch and then merge the new branch into your current branch.

3. Purposefully create and resolve a merge conflict.

Solution to

cd $(mktemp -d)
pwd
git init

for i in {1..5}
do
    echo $i >> f
    git add f; git commit -m $i
done

# 1
git branch test

# 2
git checkout test
echo test >> f
git commit f -m test
git checkout main
git log --oneline
git merge test

# 3
echo twenty >> f
git commit f -m twenty

git checkout test
echo 20 >> f
git commit f -m 20

git checkout main
git merge test

# fix conflict by editing f
# then commit

GitHub

Exercise 21

1. Create a new repository on GitHub. Clone your repository and add a README.md file. Push this file to GitHub and create a GitHub Pages website for this repository.

2. Fork an existing repository (try one of mine: seankross) and try to identify something valuable you could contribute. Make changes or additions to that repository, then open a pull request.

3. Read through GitHub’s Guides.

Solution to

In Github guides browse Connecting to GitHub with SSH to use public key authentication instead of passwords. This way you do not have to provide your password every time whenever you push your repo.