V, 54, 50 bytes
¬ ~9ñ9É 11|á
ñ2ñ20lá
ñ$18é 9ñ^y|Ehé
Pf xxywk$hP>ñd
Try it online!
Unlike usual, this program does not contain any unprintable characters.
Explanation:
¬ ~ " Insert the entire printable ASCII range
9ñ ñ " 9 times:
9É " Insert 9 spaces at the beginning of this line
11| " Move to the 11'th column on this line
á<CR> " And append a newline after the 11'th column
Now the buffer looks like this:
!
"#
$%
&'
()
*+
,-
./
01
23456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~
Now we build up the middle:
2ñ ñ " Two times:
20l " Move 20 characters to the right (because 'l' == 'right', duh)
á<CR> " Append a newline
Here's where it gets a little weird.
$ " Move to the end of this line
18é " Insert 18 spaces before the last character
9ñ " Repeat the following 9 times:
^ " Move to the first non-whitespace character
y| " Yank all the whitespace before the current character.
" We'll call this the "Leading whitespace register"
E " Move to the end of the current WORD (up to before a space)
h " Move back one character
é<CR> " And insert a newline before the current character
P " Paste the leading whitespace for indentation
f " Move forward to a space
xx " Delete two characters
" (Note how we are inbetween the two bottom branches right now)
yw " Yank everything upto the next branch (all spaces)
" We'll paste this on the line up so that we can yank it again later
" To keep track of how far apart the branches are
k$ " Move up a line and to the end of that line
hP " Move back a character and paste the whitespace we yanked
> " Indent this line by one space
ñ " End the loop
Here's an important note. The > command is actually an operator, which means it doesn't do anything without an argument, the text to operate on. For example,
>_ "Indent the current line
>> "Indent the current line
>j "Indent the current and next line
>G "Indent every line
But since this command is in a loop, we can save a character by not giving an operator. At the end of a loop, if any operator is pending it will fill in _ (the current line) as an argument implicitly.
Now I'll admit this loop is a little weird, and it can be hard to keep track of what all text should look like at any given moment. So you can use this simpler program to see what it will look like after N loops.
If you set it to 9, you can see that we have a little bit of extra text to get rid of. (Just the current line).
So we delete the current line with dd. But wait! You know how I said that operators have to take an argument which is sometime implicitly filled in? Arguments are also implicitly filled at the end of the program. So rather than dd or d_ (which are equivalent), we can simply to d and let V fill in the _ for us.
