hg fold is not intuitive

[anatoly techtonik]

I've got quite unexpected result from 'hg fold'. It looks too low level
and/or incomplete. I had this:

@  changeset:   189:43185a19a6fe
|
o changeset:   188:09ff01b1d972
|
o  changeset:   187:56687f8dd2d5
|
o  changeset:   186:bce73b522aba
|
o  changeset:   185:bc342dc49d41

And wanted to make single revision out of 186:188:
> hg fold -r 186:188

I got this:

o  changeset:   190:59975fb696ec
|  tag:         tip
|  parent:      185:bc342dc49d41
|
| @  changeset:   189:43185a19a6fe
| |
| x  changeset:   188:09ff01b1d972
| |
| x  changeset:   187:56687f8dd2d5
| |
| x  changeset:   186:bce73b522aba
|/
|

Which is not what I expected - 2 heads.

@  changeset:   189:43185a19a6fe
|
o changeset:   188:09ff01b1d972
|
o  changeset:   187:56687f8dd2d5
|
o  changeset:   186:bce73b522aba
|
o  changeset:   185:bc342dc49d41


I really hoped to see 1 head after this command.
Something like:

o  changeset:   189:43185a19a6fe
|
o  changeset:   190:59975fb696ec
|   tag:         tip
|   parent:      185:bc342dc49d41
|
|
|\
| x  changeset:   188:09ff01b1d972
| |
| x  changeset:   187:56687f8dd2d5
| |
| x  changeset:   186:bce73b522aba
|/
|

Is that possible?
In any case what should I do now to get it?
Why users are required to do this?
-- 
anatoly t.