Vim: sorting with levels - vim

Question

I have the following file with Markdown markup:
* [B](B)
* b
* c
* [C](C)
* [A](a)
* a
I try to sort it and get the following result:
* [A](a)
* a
* [B](B)
* b
* c
* [C](C)
It is necessary to sort only the main levels, and sub-levels must follow the main levels, i.e., stay at the levels where they were. The first thing that comes to mind is of course :sort; but unfortunately this will also sort the sub-levels. We will get:
* a
* b
* c
* [A](a)
* [B](B)
* [C](C)
Are there any tricks or plugins for this kind of sorting? Thx!

Answer 1

The usual approach for this class of problems is to inline each block, then sort them, and then "de-inline" them back to their original state.
First step: inline each block.
We do this by replacing each EOL followed by SPACE-SPACE-STAR with some fancy symbol unlikely to be found in our document:
:%s/\n\( \*\)/§\1
Which gives us the following:
* [B](B)§ * b§ * c
* [C](C)
* [A](a)§ * a
Second step: sort the buffer.
We simply use :help :sort:
:sort
to obtain this:
* [A](a)§ * a
* [B](B)§ * b§ * c
* [C](C)
Third step: revert each "block" to its initial state.
We do this by reverting the substitution above with another, much simpler, one:
:%s/§/\r
which gives us the desired outcome:
* [A](a)
* a
* [B](B)
* b
* c
* [C](C)
A couple of notes:
The exact pattern to use in the first substitution depends on the exact structure of your document. That part is, IMO, too highly contextual to be generalisable.
§ is just an example, use whatever symbol you want.