Rename chapters into "internals" and "intro"

levels/internals/symref-no-deref/congrats

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+Whew, we've covered a lot of things: Blobs! The index! Trees! Commits! Refs!
+
+You now know about almost everything about how Git repositories look like on the inside! We think that's pretty cool! :)
+
+Everything else is just convention and high-level commands that make interacting with the objects more convenient.
+
+We haven't covered:
+
+- tag objects (they are the fourth object type - a bit like refs with a description and an author)
+- configuration (allows you to specify remote repositories, for example)
+- working with local files (which is, uh, arguably pretty important :P)
+
+Thanks for playing! You're welcome to check out the "puzzle" levels in the dropdown, some of them are more advanced!

levels/internals/symref-no-deref/description

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+When you have a symbolic ref (a ref pointing at another ref), and you decide you want it to be a regular ref again (pointing to an object), you're in for some trouble! :)
+
+What happens when you try pointing the symbolic ref directly to the blob using `git update-ref`?
+
+Oops! Turns out that when you reference a symbolic ref, it acts as if you had specified the ref it points to. To de-symbolic-ize it, use the `--no-deref` option directly after `update-ref`!
+
+Weird, huh?

levels/internals/symref-no-deref/goal

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+git update-ref --no-deref refs/fries "$BLOB2"

levels/internals/symref-no-deref/start

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+BLOB1=$(echo delicious | git hash-object -w --stdin)
+BLOB2=$(echo very | git hash-object -w --stdin)
+git update-ref refs/curly "$BLOB1"
+git symbolic-ref refs/fries refs/curly

levels/internals/symref-no-deref/win

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+git symbolic-ref refs/fries && return 1
+test "$(git show-ref -s refs/fries)" = "035e2968dafeea08e46e8fe6743cb8123e8b9aa6"