obsolete: reports the number of local changeset obsoleted when unbundling This is a first basic visible usage of the changes tracking in the transaction. We adds a new function computing the pre-existing changesets obsoleted by a transaction and a transaction call back displaying this information. Example output: added 1 changesets with 1 changes to 1 files (+1 heads) 3 new obsolescence markers obsoleted 1 changesets The goal is to evolve the transaction summary into something bigger, gathering existing output there and adding new useful one. This patch is a good first step on this road. The new output is basic but give a user to the content of tr.changes['obsmarkers'] and give an idea of the new options we haves. I expect to revisit the message soon. The caller recording the transaction summary should also be moved into a more generic location but further refactoring is needed before it can happen.

transaction: track new obsmarkers in the 'changes' mapping The obsstore collaborate with transaction to make sure we track all the obsmarkers added during a transaction. This will be useful for various usages: hooks, caches, better output, etc. This is the seconds kind of data added to tr.changes (first one was added revisions)

configitems: register the 'progress.estimate' config