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git-training

Two factor Authentication

  • We should safeguard our git account by using two factor authentication.
  • Check out this link for more details

Using Git via SSH and HTTPS

  • When 2FA is enabled, git will ask for password for each operation. We can avoid entering password by two ways
  1. API Token
  2. SSH Key

Create an API Token

  • Create a new classic token by visiting this link
  • Enter a note and select all the scopes
  • Click on generate token and ensure you copy the token and save it somewhere

Setup an ssh key

  • Run the below commands (passphrase is optional, but it's strongly recommended)
ssh-keygen -t ed25519 -C "[email protected]"
cat ~/.ssh/id_ed25519.pub
  • Add the public key to your profile by visiting this link

gh command line

  • Install the gh command line by visiting this link

Git commands

  • Help section
git help
  • Configuring git with your data
git config --global user.name "Your Name"
git config --global user.email [email protected]
git config --global init.defaultBranch main
git config --global core.editor vim
cat ~/.gitconfig
  • Initializing a git repo (replace the value YOUR_USER_NAME with your actual user name)
mkdir random-git-repo
git init
touch README.md
git add README.md
git commit -m "initializing repo"
gh repo create --source=. --public
git push origin main

# Enter email and api token and then check the repo for your commit on Github

git clone https://github.com/YOUR_USER_NAME/random-git-repo

# See clone to a directory
# See clone and checkout a branch
  • Add a new file, commit and push
echo 'print("Hello there!")' > hello.py
python hello.py
git add hello.py
git commit -m "feat: adding hello.py"
git push origin main
  • Every push is asking for a password? If yes, export an environment variable (replace the value YOUR_API_TOKEN with your actual api token)
export GITHUB_TOKEN=YOUR_API_TOKEN
  • View current branch and checkout a new branch, check staged area using status command, check diff, commit and push
git branch
git checkout -b feature-1
echo 'print("This is feature-1!")' >> hello.py
python hello.py
git status
git diff
git add .
git commit -m "feat: adding feature-1"
git push origin feature-1
  • Switch to main branch, merge changes of feature branch, check commit logs, set upstream branch, push and delete the branch from local and remote
git switch main
git merge feature-1
python hello.py
git log
git push --set-upstream origin main
git branch -vv
git branch -d feature-1
git push origin :feature-1
  • Lets repeat adding another feature and see some more options like amending a commit message, restoring files back to original changes, restoring files from staged area and reverting commits
git branch
git checkout -b feature-2
echo 'print("This is feature-2!")' >> hello.py
echo "Hey there" > README.md
python hello.py
git status
git restore README.md
git status
echo "Hey there" > README.md
git diff
git add .
git status
git restore --staged README.md
git restore README.md
git commit -m "feat: adding feature-1"
git commit --amend -m "feat: adding feature-2"
git push origin feature-2
  • Lets add a few commits and reset back to an older commit
for i in {1..5}; do echo $i >> README.md && git commit -am "feat adding commit $i"; done
cat README.md
git log
git reset HEAD~5
git log
cat README.md
git checkout README.md
for i in {1..5}; do echo $i >> README.md && git commit -am "feat adding commit $i"; done
cat README.md
git reset HEAD~5 --hard
cat README.md

# you can also do git reset COMMIT_ID
  • Lets merge feature 2 also to main
git branch
git checkout main
git merge feature-2
python hello.py
git log
git push origin main
git branch -d feature-2
git push origin :feature-2
  • Now feature 2 has introduced a bug in production. We need to revert it from main branch and fix the bug later.
python hello.py
git revert LATEST_COMMIT_ID
python hello.py
git push origin main
git checkout HEAD~1 -b feature-2-bugfix
python hello.py
sed -i 's/This is feature-2!/This is feature-2 fixed!/g' hello.py
git status
git diff
git commit -am "fix: feature-2 bug fix"
git push origin feature-2-bugfix

# You can replace HEAD~NUMBER with actual commit hash
# For macos use
# sed -i'.bak' -e 's/This is feature-2!/This is feature-2 fixed!/g' hello.py && rm hello.py.bak
  • Lets check the difference with main branch and try to do a merge
git log
git log main
git merge main

# Lets resolve the conflict manually by editing the file and removing unnessary lines

git add hello.py
git merge --continue
git log
  • At this point, we can see we are adding unnecessary merge commits. We should avoid this and instead do a rebase.
  • Lets repeat same merge operation again with an alternate command.
  • We will abort the merge and then look at rebase.
git reset HEAD~1 --hard
git log --oneline
git log main --oneline
git pull origin main
git merge --abort
git pull origin main --rebase

# Resolve the conflicts manually
git add .
git rebase --continue
git push origin feature-2-bugfix
  • Now raise a PR from feature-2-bugfix to main branch
  • Reveiw and Merge

Working with forks

  • Adding a remote repository as upstream, checking out the upstream branch and syncing with fork
git remote add upstream [email protected]:keshavprasadms/random-git-repo.git
git remote -v
git fetch upstream
git branch -a
git checkout -b remotes/upstream/main -b upstream-main
git branch -D main
git checkout -b remotes/upstream/main -b main

# Both the below commands do the same operation
# Push from one branch to another
git push origin upstream-main:main --force

# Force push
git push origin main --force
  • After force push we lost the latest commit that was introduced by the PR. So be careful in force push.
  • Lets take the missing commit to our branch and and push again Go to the closed PR and get the commit hash
git show COMMIT_HASH
git checkout main
git log --oneline
git pull origin main --rebase
git checkout COMMIT_HASH
git push origin main
git branch
git checkout -b missing-commit
git push origin missing-commit:main
  • Lets see how we can pick some specific commits
git checkout -b branch1
git checkout -b branch2
for i in {1..5}; do echo $i >> README.md && git commit -am "feat adding commit $i"; done
git log --oneline
git checkout branch1
git show FIRST_NEW_COMMIT_HASH
git cherry-pick FIRST_NEW_COMMIT_HASH

# If you pick random in between commits, you might get merge conflicts which you can resolve manually or abort using --abort option
# Lets also take rest of the commits

git cherry-pick FIRST_NEW_COMMIT_HASH..LAST_NEW_COMMIT_HASH
  • Lets see some interactive rebase
git checkout branch2
git push origin branch
git branch --set-upstream-to=origin/branch2 branch2
git rebase -i
git log --oneline
git rebase -i HEAD~5

# Use pick for first commits
# Use squash for all other commits
# Rewrite you commit message
  • Lets create some tags
git checkout main
git log --oneline
git tag v1.0.0
git show tags/v1.0.0
git push origin tags/v1.0.0

# Check tags on UI
git checkout COMMIT_HASH_OF_FEATURE_1
git tag v0.0.1
git push origin v0.0.1

# Check tags on UI

git tag -d v0.0.1
git push origin :tags/v0.0.1
git fetch upstream --tags
  • Remove files, stash file, pop files, grep files and blame
# Remove files
rm README.md
git status
git checkout .
git rm README.md
git status
git restore --staged .
git checkout .
rm README.md

# Stash and Pop files
echo "Hey" > README.md
git checkout branch1
git stash
git checkout branch1
git checkout main
git stash pop
git stash
echo "OK" > README.md
git stash
git stash list
git stash pop --index 2
git stash show -p stash@{0}

# Grep
git grep -i "hello"
git grep -iv "hello"

# Blame
git blame hello.py

Aliases

  • Set aliases as per your liking to blaze through the command line
  • Here are a few commonly used git alises
alias g='git'
alias ga='git add'
alias gb='git branch'
alias gc='git checkout'
alias gcp="git cherry-pick"
alias gca='git commit --amend  -S -s -m'
alias gcm='git commit -S -s -m'
alias gd='git diff'
alias gfa='git fetch --all'
alias gl='git log'
alias glo='git log --graph --pretty=oneline --abbrev-commit'
alias gpl='git pull --rebase'
alias gplo='git pull --rebase origin heads/$(git rev-parse --abbrev-ref HEAD | rev | cut -d / -f1 | rev)'
alias gplu='git pull --rebase upstream heads/$(git rev-parse --abbrev-ref HEAD | rev | cut -d / -f1 | rev)'
alias gpo='git push origin $(git rev-parse --abbrev-ref HEAD)'
alias gpu='git push upstream $(git rev-parse --abbrev-ref HEAD)'
alias grb='git rebase'
alias grc='git rebase --continue'
alias grs='git rebase --skip'
alias gs='git status'
alias gst='git stash'
alias gstp='git stash pop'

Sign your commits

  • Signing your commits is always a good practice as it proves your identity
  • Follow below steps to setup signing of commits
gpg --version
# >= 2.1.17
gpg --full-generate-key

# < 2.1.17
gpg --default-new-key-algo rsa4096 --gen-key

# Enter your details
gpg --list-secret-keys --keyid-format=long

# Get the key id by looking at sec field and after /
gpg --armor --export 3AA5C34371567BD2
  • Copy your GPG key, beginning with -----BEGIN PGP PUBLIC KEY BLOCK----- and ending with -----END PGP PUBLIC KEY BLOCK-----
  • Add the key here
  • If any issues, read this doc

Raising PR using hub

  • Install hub and check it out
  • Here is a sample
hub pull-request -b USERNAME_OR_ORGANISATION/REPOSITORY_NAME:BRANCH -m "title: text" -m "description: text"
  • Example
hub pull-request -b keshavprasadms/git-training:main -m "Git training notes" -m "feat: adding training notes"

Using git on SSH

echo 'ssh-add -k ~/.ssh/id_ed25519' >> ~/.bashrc
source ~/.bashrc

# Remove the GITHUB_TOKEN environment variable and use ssh going forward

Further Exploration