phase: add a transaction argument to retractboundary We now pass a transaction option to this phase movement function. The object is currently not used by the function, but it will be in the future. All call sites have been updated. Most call sites were already enclosed in a transaction for a long time. The handful of others have been recently updated in previous commit.

phase: add a transaction argument to advanceboundary We now pass a transaction option to this phase movement function. The object is currently not used by the function, but it will be in the future. All call sites have been updated. Most call sites were already enclosed in a transaction for a long time. The handful of others have been recently updated in previous commit. The retractboundary function remains to be upgraded.

pull: pre-filter remote phases before moving local ones We were relying on the phase internals to filter out redundant phase information from remove. However as we plan to integrate phase movement inside the transaction, we want to avoid useless transaction creation on no-op pulls. Therefore we filter out all the information that already matches the current repository state. This will let us create a transaction only when there is actual phase movement needed.