Git: How to rebase a feature branch that is based on another feature branch onto master?

My git history looks like this:

 A     B    main
 |     |    | 
 *     |    |
 *     |    |
 *     |    |
   \   |    |
     \ |    |
       *    |
       *    |
        \   |
          \ |
           \|

What I want something like this:

B   main A
|  |   |
|  |   |
|  |   |
|  |   |
|  |   |
|  |   *
*  |   *
*  |   *
\  |  /
 \ | /

When I tried rebasing A onto main, it rebased B. The main issue is that I have things on A, that are dependent on B, but I would like to keep those changes on B. Is this possible?

Thanks in advance.

Solution

So redrawing with named commits so it is possible to refer to them individually.

  a3 - <A>
   \
    a2
     \
      a1
       \  b2 - <B>
        \ |
         b1 
          \ 
           m35 - <main>
            |
           m34
            |
           ...

What you want is

  a3' - <A>
   \
    a2'
     \       b2 - <B>
      a1'     |
       \     b1
        \   /
         m35 - <main>
          |
         m34
          |
         ...

where a1' is commit a1 rebased on top of main but excluding the changes from commit b1, etc.

This is as Phillip commented a prime use case for rebase --onto, namely in this case

git rebase --onto main b1 A  # where "b1" is the actual commit id for commit b1

PS When running (non-interactive) rebase you should exclusively use the 2 or 3 argument form.