obsstore: record data as floating point in fm0 format For python struct module, "d" is double. But for python string formating, "d" is integer. We want to preserve the floating point nature of the data, so we store it in the metadata as floating point. We use "%r" to make sure we get as many significant digitis as necessary to restore the float to the exact same value on the other side. The fm1 is transmitting the information as float. The lack of this made fm1-stored markers not survive a round-trip to fm0 leading to duplicated markers (or two markers very alike).

bundle2: add a comment about addchangegroup source and url

pull: call the `b2x-transactionclose` hook when closing the transaction We need a wider set of hooks to process all the changes that happened during the pull transaction. We reuse the experimental `b2x-transactionclose` hook set from server's unbundle for consistency. This hook is experimental and will not remains as-is forever, but this will open the door for experimentation in 3.2.

revset-only: use __nonzero__ to check if a revset is empty For some smartsets, computing length is more expensive than checking if the set is empty.