Rework levels, and add some new ones

levels/blob-create/description

@@ -9,3 +9,7 @@ Let's create some blobs! To do that, create a file with the desired content, and
 The flag -w means "write", and tells Git to actually write the new blob to the disk.
 
 Create three new blobs!
+
+Tip: you can also use a command like this to create a blob in a single line:
+
+    $ echo "awesome content" | git hash-object -w --stdin

levels/blob-remove/description

@@ -0,0 +1,5 @@
+There's a simple command to remove all blobs that are not connected to anything:
+
+    $ git prune
+
+Remove all blobs in this repository.

levels/blob-remove/goal

@@ -0,0 +1 @@
+git prune

levels/blob-remove/start

@@ -0,0 +1,3 @@
+echo "My master password is a1b2c3d4e5" | git hash-object -w --stdin
+echo "This blob really should not exist" | git hash-object -w --stdin
+echo "This is a virus" | git hash-object -w --stdin

levels/blob-remove/win

@@ -0,0 +1,3 @@
+OBJECT_COUNT=$(git cat-file --batch-check='%(objectname) %(objecttype)' --batch-all-objects | wc -l)
+
+test "$OBJECT_COUNT" -eq 0

levels/commit-parents/description

@@ -2,4 +2,6 @@ When using the commit-tree command, you can optionally specify a parent:
 
     $ git commit-tree <tree> -m "Description" -p <parent commit>
 
-Can you make a string of three commits? We placed an empty tree in your repo to get you started.
+Make a string of three commits!
+
+Hint: What would be the easiest way to get a tree object?

levels/commit-parents/goal

@@ -1,3 +1,4 @@
+git write-tree
 FIRST_COMMIT=$(git commit-tree 4b82 -m 'First commit :O')
 SECOND_COMMIT=$(git commit-tree 4b82 -p $FIRST_COMMIT -m 'Second commit :D')
 THIRD_COMMIT=$(git commit-tree 4b82 -p $SECOND_COMMIT -m 'Third commit \o/')

levels/commit-parents/start

@@ -1 +0,0 @@
-git write-tree

levels/index-add/description

@@ -0,0 +1,10 @@
+Blobs usually represent the content of a file. But on their own, they don't have any metadata, not even a name!
+
+Git has a very powerful concept to store metadata related to blobs: the index! It's a list that relates blobs to filenames and permissions.
+
+Even though it is possible to add an entry directly to the index, it's much more convenient to do it via an existing file:
+
+    $ echo "my content" > file
+    $ git update-index --add file
+
+Add three entries to the index! For a bonus challenge: can you add a file that is inside of a directory, like "directory/file"?

levels/index-add/goal

@@ -0,0 +1,4 @@
+echo "file 1" > file1
+echo "file 2" > file2
+echo "file 3" > file3
+git add .

levels/index-add/win

@@ -0,0 +1 @@
+test "$(git ls-files | wc -l)" -ge 3

levels/index-remove/description

@@ -0,0 +1,5 @@
+To remove an entry from the index, use a command like this:
+
+    $ git update-index --force-remove <file>
+
+Remove all entries from the index!

levels/index-remove/goal

@@ -0,0 +1,3 @@
+git update-index --force-remove file1
+git update-index --force-remove file2
+git update-index --force-remove file3

levels/index-remove/start

@@ -0,0 +1,4 @@
+echo "file 1" > file1
+echo "file 2" > file2
+echo "file 3" > file3
+git add .

levels/index-remove/win

@@ -0,0 +1 @@
+test "$(git ls-files | wc -l)" -eq 0

levels/index-update/description

@@ -0,0 +1,9 @@
+Instead of removing an entry from the index and adding one with the same name, you can also directly update that entry!
+
+Put the content you want in a file with a matching name, and then run
+
+    $ git update-index <file>
+
+This will create a new blob, and update the hash of the entry to that blob.
+
+Update an entry in the index!

levels/index-update/goal

@@ -0,0 +1,2 @@
+echo "new content" > file1
+git update-index file1

levels/index-update/start

@@ -0,0 +1,4 @@
+echo "file 1" > file1
+echo "file 2" > file2
+echo "file 3" > file3
+git add .

levels/index-update/win

@@ -0,0 +1 @@
+test "$(git ls-files | wc -l)" -eq 0

levels/ref-create/description

@@ -1,9 +1,9 @@
-Let's take a look at "refs", short for "references"! Refs are not objects, but rather very simple *pointers* to objects! They can help you keep track of what's where.
+Let's take a look at "refs" (short for "references")! Refs are not objects, but rather very simple *pointers* to objects! They can help you keep track of what's where.
 
 You can create or update a ref with
 
     git update-ref refs/<refname> <newvalue>
 
-Make sure to start a ref's name with "refs/"! That's a convention that helps Git find all refs you create.
+Make sure to always start a ref's name with "refs/"! That's a convention that helps Git find all refs you create. If you forget the "refs/", you will not see the ref.
 
 Create refs that point to all objects in this repository!

levels/ref-move/description

@@ -0,0 +1,5 @@
+You can point refs to a new location using the same command you use to create them:
+
+    git update-ref refs/<refname> <object>
+
+As an exercise, make all refs in this repository point to the tree object!

levels/ref-move/goal

@@ -0,0 +1,3 @@
+for REF in $(git for-each-ref --format='%(refname)'); do
+    git update-ref "$REF" "$TREE"
+done

levels/ref-move/start

@@ -0,0 +1,10 @@
+echo hello > hello
+echo world > world
+BLOB1=$(git hash-object -w hello)
+BLOB2=$(git hash-object -w world)
+git add .
+TREE=$(git write-tree)
+COMMIT=$(git commit-tree $TREE -m "Initial commit")
+
+git update-ref refs/a "$BLOB1"
+git update-ref refs/b "$COMMIT"

levels/ref-move/win

@@ -0,0 +1 @@
+test "$(git show-ref -s | uniq)" = "c7863f72467ed8dd44f4b8ffdb8b57ca7d91dc9e"

levels/ref-remove/description

@@ -0,0 +1,5 @@
+To delete a ref, use
+
+    git update-ref -d refs/<refname>
+
+Delete all refs! :P

levels/ref-remove/goal

@@ -0,0 +1,3 @@
+for REF in $(git for-each-ref --format='%(refname)'); do
+    git update-ref -d "$REF"
+done

levels/ref-remove/start

@@ -0,0 +1,10 @@
+echo hello > hello
+echo world > world
+BLOB1=$(git hash-object -w hello)
+BLOB2=$(git hash-object -w world)
+git add .
+TREE=$(git write-tree)
+COMMIT=$(git commit-tree $TREE -m "Initial commit")
+
+git update-ref refs/best_blob_ever "$BLOB1"
+git update-ref refs/beautiful_commit "$COMMIT"

levels/ref-remove/win

@@ -0,0 +1 @@
+test "$(git show-ref | wc -l)" -eq 0

levels/symref-create/description

@@ -4,6 +4,4 @@ When that happens, they are called "symbolic refs". You can create or update a s
 
     git symbolic-ref <name> <ref>
 
-Usually, you will only encounter a special symbolic ref called "HEAD". This ref is special in that it doesn't start with "refs/"! You might already have seen it in the other levels - it's the only thing that's always there!
-
-Try pointing HEAD to the refs in this repository!
+Create a symbolic ref called "refs/rainbow"!

levels/symref-create/goal

@@ -1 +1,3 @@
-git symbolic-ref HEAD refs/best_commit
+BLOB=$(git hash-object -w --stdin)
+git update-ref refs/double "$BLOB"
+git symbolic-ref refs/rainbow refs/double

levels/symref-create/start

@@ -1,4 +0,0 @@
-TREE=$(git write-tree)
-COMMIT=$(git commit-tree $TREE -m "Initial commit")
-git update-ref refs/best_commit $COMMIT
-git update-ref refs/worst_commit $COMMIT

levels/symref-create/win

@@ -1 +1 @@
-git symbolic-ref HEAD | grep _commit
+git symbolic-ref refs/rainbow

levels/symref-no-deref/description

@@ -0,0 +1,7 @@
+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/symref-no-deref/goal

@@ -0,0 +1 @@
+git update-ref --no-deref refs/fries "$BLOB2"

levels/symref-no-deref/start

@@ -0,0 +1,4 @@
+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/symref-no-deref/win

@@ -0,0 +1,2 @@
+git symbolic-ref refs/fries && exit 1
+test "$(git show-ref -s refs/fries)" = "035e2968dafeea08e46e8fe6743cb8123e8b9aa6"

levels/tree-create/description

@@ -1,21 +1,7 @@
-Blobs just have some content and an ID. It would be convenient to be able to give names to a blob, right?
+After carefully building the index we want, it would be nice to save a permanent snapshot of it, right?
 
-The second type of Git object is called a "tree" - a tree points a bunch of blobs, and gives each of them a name!
-
-How can we build our own trees? Introducing: the index!
-
-The index is like a "work in progress" version of a tree, where we can add and remove blobs. When we're happy with what we have built, we can make it into a real tree object!
-
-We can use
-
-    $ git update-index --add <file>
-
-to make the file's content into a blob, and to add that blob to the index using the file's name.
-
-When we're happy with out index, we can convert it into a tree using
+This is what the second type of objects is for: trees! You can convert the index into a tree using
 
     $ git write-tree
 
-That command will output the ID of the newly crated tree.
-
-Build a tree containing just the 'noises' file, which we conveniently placed in your current directory! :)
+Try it! :)

levels/tree-create/goal

@@ -1,5 +1 @@
-git update-index --add noises
 git write-tree
-
-rm noises
-git update-index --remove noises

levels/tree-create/start

@@ -1 +1,4 @@
-echo 'meow' > noises
+echo "file 1" > file1
+echo "file 2" > file2
+echo "file 3" > file3
+git add .

levels/tree-create/win

@@ -1 +1 @@
-git cat-file -p c099013035060f20e8d8f5db69e158213fbec519
+git cat-file -p 21a638f28022064c1f1df20844278b494d197979

levels/tree-nested/description

@@ -1,5 +1,5 @@
-Trees can also point to other trees! This way, they can basically describe nested directory structures.
+Trees can also point to other trees! This way, they can describe nested directory structures.
 
-When you add a file inside of a directory to the index, and then call `git write-tree`, it will automatically do the correct thing.
+When you add a file inside of a directory to the index, and then call `git write-tree`, it will create a nested tree for the directory, and attach the blob to it.
 
-To solve this level, build a little stick figure, as shown on the left - a tree that points to two blobs, and to a tree that points to two blobs.
+To solve this level, build a little stick figure, as shown on the left - a tree that points to two blobs, as well to a tree that points to two blobs.

levels/tree-read/description

@@ -0,0 +1,5 @@
+As soon as you have some tree objects, you can always read them and set the index exactly to their content! Unsurprisingly, the command is called
+
+    $ git read-tree <tree>
+
+Try switching between the trees in this repository!

levels/tree-read/goal

@@ -0,0 +1 @@
+git read-tree "$TRIPLE_TREE"

levels/tree-read/start

@@ -0,0 +1,15 @@
+EMPTY_TREE=$(git write-tree)
+
+echo "file 1" > file1
+echo "file 2" > file2
+git add .
+git write-tree
+
+rm *
+echo "file A" > fileA
+echo "file B" > fileB
+echo "file C" > fileC
+git add .
+TRIPLE_TREE=$(git write-tree)
+
+git read-tree "$EMPTY_TREE"

levels/tree-read/win

@@ -0,0 +1 @@
+test "$(git ls-files | wc -l)" -gt 0

levels/welcome/description

@@ -0,0 +1,7 @@
+To the left, you see an empty Git repository!
+
+The only thing that's always there is the HEAD reference - we'll look at what that is later.
+
+You can drag and drop all nodes on the left, and reorder them how you want!
+
+You can enter Bash commands in the line at the bottom.