`git rebase -i --rebase-merges` formatting

Hello,

for the following commits:

``` git log
*   4fd94fd  (HEAD -> master) 6 hours ago Jan Christoph Uhde Merge branch 'b_two'
|\
| * cc75466  6 hours ago Jan Christoph Uhde b_two
|/
*   9ad8a2b  6 hours ago Jan Christoph Uhde Merge branch 'b_one'
|\
| * b23658f  (b_one) 6 hours ago Jan Christoph Uhde one
|/
* a9d65bc  6 hours ago Jan Christoph Uhde initial commit
```

I get a this merge script when rebasing onto the initial commit.

``` actual merge script
   1 label onto
   2
   3 # Branch b-one
   4 reset onto
   5 pick b23658f one
   6 label b-one
   7
   8 # Branch b-two
   9 reset onto
  10 merge -C 9ad8a2b b-one # Merge branch 'b_one'
  11 label branch-point
  12 pick cc75466 b_two
  13 label b-two
  14
  15 reset branch-point # Merge branch 'b_one'
  16 merge -C 4fd94fd b-two # Merge branch 'b_two'
  17
  18 # Rebase a9d65bc..4fd94fd onto a9d65bc (11 commands)
  19 #
```

I think it should be more similar to this:

``` suggested merge script
   1 label onto
   2 reset onto #Could imo go but probably avoids special cases
   3
   4 # Branch b-one
   5 pick b23658f one
   6 label b-one
   7 reset onto
   8 merge -C 9ad8a2b b-one # Merge branch 'b_one'
   9 label branch-point
  10
  11 # Branch b-two
  12 pick cc75466 b_two
  13 label b-two
  14 reset branch-point # Merge branch 'b_one'
  15 merge -C 4fd94fd b-two # Merge branch 'b_two'
  16 # add `label branch-point-1` here to avoid special cases?!
  17
  18 # Rebase a9d65bc..4fd94fd onto a9d65bc (11 commands)
  19 #
```

Looking at the sequencer.c it might not be worth the invested time to change the format. If it can not be resolved easily I think removing the empty lines and the branch-comments would suffice to reduce the confusion. I think they have been introduced to help people but here they are a hindrance.

Another unrelated suggestion is to start with `branch-point-0` instead of `onto` and keep counting up. This would make the edit-distances smaller when you fiddle with the first commits.

Regards

Jan