This is done because at places in hgsubversion, we call the function directly. I
expect there might be more instances in extensions out there which calls
commands.push() directly. So let's not require explicitly passing of bookmark
value.
The use of opts['bookmark'] was introduced in
bad05a6afdc89cc58a2af320698ab29bd8de62d4.
@yuja this one? I thought if the above condition is true, this will be fine, but now I see or rev.