puzzling revision history

Nothing urgent here. monotone-viz is reporting a puzzling revision 
history, and I'mtryngtofigure out howit could have arisen with the 
rather pedestrian operations I use.

d40c1d1e  branches C and priority
    |
    V
0d0fb542  branch priority
    |
    V
e388aa8b  branch priority
    |
    V
ebf87897  branches C and priority

Well, obviously branches C and priority had been tightly synchronised 
at d40c1d1e, development took place on the priority branch only for a 
few revisions, and then it was merged back to the C branch to 
synchronise them again.

This is all pretry straightforward stuff.

But why is there no arrow from d40c1d1e to ebf87897 and a little merge 
circle?


Isn't ebf87897 a merge between d40c1d1e and e388aa8b?

-- hendrik