Work on the intro and the index chapter

levels/unused/checkout

@@ -0,0 +1,31 @@
+title = Getting the last version
+cards = checkout-file
+
+[description]
+
+You've been working on your essay for a while. But - ughh! Now your cat walks over your keyboard and "helps you", so now it's all messed up! :/
+
+But Git is here to help! To discard all changes your cat made, and go back to the version in the last commit, use `checkout`!
+
+[setup]
+
+echo "A" >> essay.txt
+git add .
+git commit -m "Initial commit"
+
+echo "B" >> essay.txt
+git commit -a -m "Improved version"
+
+echo "C" >> essay.txt
+git commit -a -m "Even better version"
+
+echo "D" >> essay.txt
+git commit -a -m "Marvelous version"
+
+echo "blarg
+blaaaargh" > essay.txt
+
+[win]
+
+# Restore the version from the last commit.
+cat essay.txt | grep D

levels/unused/checkout-commit

@@ -0,0 +1,44 @@
+title = Moving through time
+cards = checkout commit-auto
+
+[description]
+
+The yellow boxes are frozen points in time, we call them "commits"! You can travel between them using the "checkout" card! (Try it!)
+
+The grey panel below shows your current environment - click on an object to inspect or modify it!
+
+Can you find out what happened here? Then, come back to the latest commit, and fix the problem, using the "commit" card!
+
+[setup]
+
+mkdir room1 room2
+echo "A young girl with brown, curly hair." > room1/little_sister
+echo "This piggy bank belongs to the big sister.
+It contains 10 coins." > room2/piggy_bank
+git add .
+git commit -m "The beginning"
+
+mv room1/little_sister room2
+git add .
+git commit -m "Little sister walks over"
+
+echo "Has 10 coins." >> room2/little_sister
+echo "This piggy bank belongs to the big sister.
+It is empty." > room2/piggy_bank
+git add .
+git commit -m "Little sister does something"
+
+mv room2/little_sister room1
+git add .
+git commit -m "Little sister walks back"
+
+git checkout --detach
+git branch -d main
+
+[win]
+
+{ git show HEAD:room2/piggy_bank | grep "10 coins"; } && { git show HEAD:room1/little_sister | grep -v "10 coins"; } && { git rev-parse HEAD^; }
+
+[congrats]
+
+Wonderful! Now that you're getting familiar with the time machine, let's look at some more complicated situations...

levels/unused/clone

@@ -0,0 +1,20 @@
+title = Cloning a repo
+cards = clone commit-auto pull push
+
+[description]
+
+Get your friend's repo using clone, change something, push it back.
+
+[setup]
+
+rm -rf .git
+
+[setup friend]
+
+echo hi > file
+git add .
+git commit -m "Initial commit"
+
+[win friend]
+
+test "$(git show main:file)" != hi

levels/unused/commit

@@ -0,0 +1,27 @@
+title = Make a commit \o/
+cards = add reset checkout commit
+
+[description]
+
+For practice, make a commit where all files contain an "x"!
+
+[setup]
+
+echo a > a
+echo x > b
+echo x > c
+git add .
+git commit -m "Initial commit"
+echo x > a
+echo b > b
+git add b
+echo c > c
+
+[win]
+
+# File a contains "x" in the last main commit.
+test "$(git show main:a)" = x
+# File b contains "x" in the last main commit.
+test "$(git show main:b)" = x
+# File c contains "x" in the last main commit.
+test "$(git show main:c)" = x

levels/unused/commit-a

@@ -0,0 +1,26 @@
+title = Make a commit, but faster!
+cards = add reset checkout commit commit-a
+
+[description]
+
+There is a time-saving trick, where instead of a plain `git commit`, you can use
+
+    git commit -a
+
+This will automatically add all changes you made to local files! Very convenient.
+
+[setup]
+
+echo a > a
+echo b > b
+echo c > c
+git add .
+git commit -m "Initial commit"
+echo x > a
+echo x > b
+echo x > c
+
+[win]
+
+# Make a commit where all files contain "x".
+test "$(git show main:a)" = x && test "$(git show main:b)" = x && test "$(git show main:c)" = x

levels/unused/init

@@ -0,0 +1,14 @@
+title = Welcome!
+cards = init
+
+[description]
+
+
+[setup]
+
+rm -rf .git
+
+[win]
+
+# Again, initialize your time machine!
+test -d .git

levels/unused/restore

@@ -0,0 +1,28 @@
+title = Looking into the past
+cards = checkout-from
+
+[description]
+
+You've been working on your essay for a while. But you're not happy with the changes you've made recently. You want to go back to the version called "Best version"!
+
+No problem, you can use the `checkout` card to restore your essay from an older commit!
+
+[setup]
+
+echo "Initial version" > essay.txt
+git add .
+git commit -m "Initial commit"
+
+echo "Improved version" > essay.txt
+git commit -a -m "Improved version"
+
+echo "Best version" > essay.txt
+git commit -a -m "Best version"
+
+echo "Less-good version" > essay.txt
+git commit -a -m "Less-good version"
+
+[win]
+
+# For nostalgic reasons, restore the very first backup you made!
+diff essay.txt <(echo "Best version")

levels/unused/who-are-you

@@ -0,0 +1,23 @@
+title = Nice to meet you!
+cards = config-name config-email
+
+[description]
+
+Introduce yourself using
+
+    git config --global user.name Firstname
+    git config --global user.email "your@mail.com"
+
+[setup]
+
+[actions]
+
+test "$(git config user.name)" != "You" && hint "Hey $(git config user.name), nice to meet you!"
+
+[win]
+
+# Have a name configured.
+test "$(git config user.name)" != "You"
+
+# Have an email address configured.
+test "$(git config user.email)" != "you@time.agency"