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Git Hands-On Workshop

0. PowerShell Prep

# Let's teach PowerShell some macOS commands

# 1. `touch <file>` creates an empty file
function touch ($Path) { Add-Content $Path $null }
# 2. `open <path>` opens Explorer/Finder
Set-Alias open start

1. Help

git help                        # General help
git help --guide                # Common Git guides

2. Configuration

git help config                 # See FILES section
git config --global --list      # ~/.gitconfig

# Check specific config values
git config user.name
git config user.email

git config --global user.email git@example.com

git config --global --edit      # Open config in editor

3. Git 101

# Change to location of your choice
# ...so we can make directory for today
mkdir git-hands-on
cd git-hands-on

# Let's create a new repository
git init git101
# Can also `git init` directory that already exists

# Let's see what we have
cd git101
ls .git
open .

# Of particular note:
# - .git/objects/               (empty)
# - .git/refs/heads/            (empty)
# - .git/config                 `git config -e`
# - .git/HEAD                   ref: refs/heads/master

# What does Git think it has?
git status

# Let's commit something!
touch README.md                 # Create README.md
git status                      # Untracked files!

git add -A                      # Track all changes
git status                      # Changes!

    # <internals>
    ls .git/objects/
    ls .git/objects/e6/
    git cat-file -t e69de29bb2d1d6434b8b
    # </internals>

git commit -m "Add empty README"

    # <internals>
    git cat-file -t f93e3a1a1525fb5b9102
    git cat-file -p f93e3a1a1525fb5b9102

    cat .git/HEAD
    ls .git/refs/heads/
    cat .git/refs/heads/master

    git rev-parse HEAD
    git cat-file -p $(git rev-parse HEAD)
    # </internals>

git show HEAD
git log

Git 101 Summary

  1. Make changes
  2. Track changes: git add -A
  3. Commit changes: git commit -m "Do something"

4. Clone a Remote Repository

cd ..
git clone https://github.com/dahlbyk/git-hands-on.git katas

# Let's see what we have
cd katas
ls .git
open .

# What does Git think it has?
git status

    # <internals>
    git cat-file -p $(git rev-parse HEAD)
    git cat-file -p "HEAD^{tree}"
    git cat-file -p 176a458f94e0ea5272ce
    # </internals>

# What local branches do we have?
git branch

# What is 'origin/gh-pages'?
git remote -v
git branch -r

# What does it mean by "up-to-date"?
# Local matches remote "upstream" or "tracked" branch.
git config branch.gh-pages.remote
git config branch.gh-pages.merge

# Big picture?
gitk

5. Push to a Remote Repository

# Edit this line: my favorite number is π
git commit -am "Fix favorite number"

git status                      # Branch is ahead

gitk
git log --oneline --graph --decorate

# <aside>
# Git has a few push modes, but the best is:
git config --global push.default upstream
# </asid

# Let's share our favorite number
git push

Oops! That didn't work because you don't have permission to push.

  1. Create a GitHub account and sign in

  2. From this project on GitHub, click the Fork button

  3. Once forking is complete, click the Clone or download button and copy the HTTPS URL (e.g. https://github.com/coridrew/git-hands-on.git)

# Now let's point origin at your fork
git remote set-url origin https://github.com/coridrew/git-hands-on.git

# And try pushing again
git push

6. Working Locally with Branches

# Start work on feature 1
git branch feature1             # Create branch from here
git checkout feature1           # Switch to different branch

    # <internals>
    cat .git/HEAD
    cat .git/refs/heads/feature1
    # <internals>

git status
touch feature1.md
git add .
git commit -m "Add feature 1"

    # <internals>
    cat .git/HEAD
    cat .git/refs/heads/feature1
    # <internals>

# Start work on feature 2
touch feature2.md
git add .
git status

# Oops, forgot to switch to new branch
git checkout gh-pages -q
git checkout -b feature2
git commit -m "Add feature 2"

gitk --branches

# Start work on feature 3
git checkout gh-pages -b feature3
touch feature3.md
# Get distracted by feature 4
touch feature4.md

# Oops, forgot to commit feature 3!
git add .
git status

# Don't want to commit everything...
git reset feature4.md           # reset path is opposite of add
git status
git commit -m "Add feature 3"

git checkout gh-pages -b feature4
git add .
git commit -m "Add feature 4"

gitk --branches

7. Working Remotely with Branches

# First, let's add a remote for the parent repository...
git remote add upstream https://github.com/dahlbyk/git-hands-on.git

    # <internals>
    ls .git/refs/remotes/
    # </internals>

# ...and get latest from GitHub
git fetch --all

    # <internals>
    ls .git/refs/remotes/upstream/
    cat .git/refs/remotes/upstream/gh-pages
    # </internals>

# Now let's share some code!
git push origin feature1

# We can also push the current branch
git push origin HEAD

# But notice we're missing "up-to-date"
git status

# And plain `git push` fails
git push

# Add -u to set the local branch's upstream
git push -u origin HEAD
git status

# Now plain `git push` works
git push

# Also, typing is overrated (pc = push current)
git config --global alias.pc "push -u origin HEAD"
git pc

# Now let's pretend someone else is working
# On your fork on GitHub:
# 1. Use **Branch** dropdown to create `feature5`
# 2. Use **Branch** dropdown to switch to feature1
# 3. Click on `feature1.md`, then the pencil to edit
# 4. Change something and commit changes directly to `feature1`
# 5. Use Branches list to delete `feature4`

# Nothing changes until we explicitly fetch:
git branch -r
git fetch --all

# Why doesn't feature4 show as deleted?
git remote prune origin
git fetch --prune --all

# Always want to prune?
# git config fetch.prune = true
# git config remote.<name>.prune = true

# But we're still on feature4...interesting
git status                      # upstream is gone!
git branch -d feature4
git branch -D feature4

# We should also bring in changes from feature1
git checkout feature1
git status                      # behind!
git pull                        # get latest & merge

# Finally, let's work on feature5
git checkout --track origin/feature5

# Too much typing...let's try again
git checkout master
git branch -D feature5

# If a branch only exists on one remote,
# Git will do the right thing
git checkout feature5

# Now let's add a file and push
touch feature5
git add .
git commit -m "Add feature5"
git push
# Note that `git push` Just Works™

8. Merging

# When we pulled from `feature1` we saw "Fast-forward"
# What does that mean? Let's try again.
git checkout feature1

# reset can also move HEAD (i.e. your branch) around
# In this case, we move HEAD back one, to its parent
# (See `git help revisions` for more tricks like ~)
git reset --hard HEAD~

# Now let's look at the commit graph
gitk feature1 origin/feature1

# Because local feature1 has nothing new, Git can fast-forward
# But you can force it to create a merge commit
git merge --no-ff origin/feature1

# We can also merge local branches
git merge feature2

# And even multiple branches at once ("octopus merge")
git reset --hard HEAD~2
git merge origin/feature1 feature2 feature3

9. Katas

katas branch has its own readme!

git checkout katas