Add all new levels

levels/experiments/commit

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+title = "fu"
+
+[description]
+
+So you've been working on a project for a while, and decide you want to put it in a Git repository.
+
+Here's how to do it! First, you initialize a new Git repository in your current directory:
+
+    git init
+
+Then say that you want to record the current state of all files:
+
+    git add .
+
+And then you make a commit, which gives the current state a description, a date, and your name:
+
+    git commit
+
+[setup]
+
+mkdir recipes
+echo -e "blueberries\nflour" > recipes/blueberry_cake.txt
+echo -e "water\ncarrots" > recipes/carrot soup.txt
+echo "Very good recipes!" > README.md
+
+[win]
+
+test "$(git rev-parse HEAD^{tree})" = 1e02e3151284d0e22cd9b07ca5c5dbae2f3cb521

levels/experiments/pull-merge-push

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+title = A pull and a conflict
+author = blinry
+
+[description]
+
+You want to push your new commits to the server, but someone has already pushed their own changes.
+
+In this situation, you need to pull first! Try that here - you'll have to resolve a merge conflict. Push your changes afterwards.
+
+[congrats]
+
+Good job! Here's some additional info: banana!
+
+[setup yours]
+
+echo fu > file
+git add .
+git commit -m "Initial commit"
+git push
+
+echo fi > file
+git commit -a -m "Fi is good"
+
+[setup origin]
+
+echo fa > file
+git add .
+git commit -a -m "Fa is good"
+
+[win origin]
+
+test "$(git rev-parse HEAD^1^)" = "$(git rev-parse HEAD^2^)"

levels/experiments/rebase

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+description = Rebase all branches on top of the main branch, so that the commits are in alphabetical order, and then point the main branch to the top commit.
+
+[setup]
+
+git commit --allow-empty -m A
+git commit --allow-empty -m B
+git commit --allow-empty -m C
+
+git switch -c side1 main~1
+git commit --allow-empty -m D
+git commit --allow-empty -m E
+
+git switch -c side2 main~2
+git commit --allow-empty -m F
+
+git checkout main
+
+[win]
+
+diff <(git log --pretty=%s main) <(echo -e "F\nE\nD\nC\nB\nA")

levels/experiments/sandbox

@@ -0,0 +1,8 @@
+[setup local]
+
+git commit --allow-empty -m "1"
+git commit --allow-empty -m "2"
+git commit --allow-empty -m "3"
+git push
+
+[setup origin]

levels/intro/motivation

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+[description]
+
+So you've been working on an essay about goldfish. You can look at the backup copies you made by clicking on them!
+
+But look - something went wrong in the latest version of the file! Maybe it has been infected with a vowel-eating virus?
+
+Make a new version (with the number 5) from the last version that's still okay, and add at least two more lines to it!
+
+[congrats]
+
+Good that you had that backup, huh?
+
+But you're a bit worried that two weeks from now, you'll have hundreds of copies of your essay, and it will be hard to keep track of all of them.
+
+And especially when working with other people, sending backup copies around doesn't seem ideal.
+
+Let's look at another way to do this. :) Click "Next Level" as soon as you're ready!
+
+[setup]
+
+rm -rf .git
+
+echo "~ Why goldfish are the best pets ~
+
+(I still need to write this.)" >> essay_1.txt
+
+
+echo "~ Why goldfish are the best pets ~
+
+- They don't make any noise.
+- They are pretty. (I should probably put this higher in the list?)" >> essay_2.txt
+
+
+echo "~ Why goldfish are the best pets ~
+
+- They are pretty.
+- They don't pee on the carpet.
+- They don't make any noise." >> essay_3.txt
+
+echo "~ Why gldfsh r th bst pts ~
+
+- Thy r prtty.
+- Thy dn't p n th crpt.
+- Thy dn't mk ny ns." >> essay_4.txt
+
+[win]
+
+test "$(cat *5.txt | wc -l )" -ge 7 && grep carpet *5.txt

levels/intro/restore

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+[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 again! :/
+
+To restore your essay from the last backup, type:
+
+    git restore essay.txt
+
+To restore an older version, for example, from two backups before the latest one, type:
+
+    git restore -s HEAD~2 essay.txt
+
+For nostalgic reasons, restore the very first backup you made!
+
+[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]
+
+diff essay.txt <(echo "A")

levels/intro/setup

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+[description]
+
+One month later, you're woking on an essay about tardigrades!
+
+This time, a friend has recommended that you use the version control system Git to keep backups of your file.
+
+Currently, your directory only contains your essay. To initialize a Git repository in your directory, type:
+
+    git init
+
+Then, each time you want to make a backup, type:
+
+    git add essay.txt
+    git commit
+
+Enter a description of what you changed in the editor that opens and click save.
+
+That way, you've made a backup of the current version of the file. Then add at least two more lines, and make another backup by repeating the add and the commit commands.
+
+[setup]
+
+rm -rf .git
+
+echo "~ Why tardigrades are cool ~
+
+- They can survive in space.
+- They are resistant to extreme heat and cold." > essay.txt
+
+[win]
+
+test -d .git && git rev-parse HEAD^ && test "$(git show HEAD:essay.txt | wc -l)" -ge 6