caches: introduce a function to warm cache We have multiple caches that gain from being kept up to date. For example in a server setup, we want to make sure the branchcache cache is hot for other read-only clients. Right now each cache tries to update themself in place where new data have been added. However the approach is error prone (we might miss some spot) and fragile. When nested transaction are involved, such cache updates might happen before a top level transaction is committed. Writing caches for uncommitted data on disk. Having a single entry point, run at the end of each successful transaction, helps to ensure the cache is up to date and refreshed at the right time. We start with updating the branchmap cache but other will come.

transaction: track newly introduced revisions Tracking revisions is not the data that will unlock the most new capability. However, they are the simplest thing to track and still unlock some nice improvements in regard with caching. We plug ourself at the changelog level to make sure we do not miss any revision additions. The 'revs' set is configured at the repository level because the transaction itself does not needs to know that much about the business logic.

transaction: introduce "changes" dictionary to precisely track updates The transaction is already tracking some data intended for hooks (in 'hookargs'). However, that information is minimal as we optimise for passing data to other processes through environment variables. There are multiple places were we could use more complete and lower level information locally (eg: cache update, better report of changes to hooks, etc...). For this purpose we introduces a 'changes' dictionary on the transaction. It is intended to track every changes happening to the repository (eg: new revs, bookmarks move, phases move, obs-markers, etc). For now we just adds the 'changes' dictionary. We'll adds more tracking and usages over time.

clone: add a server-side option to disable full getbundles (pull-based clones) For large enough repositories, pull-based clones take too long, and an attempt to use them indicates some sort of configuration or other issue or maybe an outdated Mercurial. Add a config option to disable them.

clone: warn when streaming was requested but couldn't be performed This helps both users and the people who support them figure out why a stream clone couldn't be performed. In an upcoming patch we're going to add a way for servers to hard abort on a full getbundle. In those cases servers might expect clients to perform a stream clone, so it's important to communicate why one couldn't be done.

clone: test streaming disabled because client is missing requirement Turns out we had no coverage for this important case.

bundle2: don't check for whether we can do stream clones At the moment this isn't used and all stream clones use the legacy protocol. In an upcoming diff, canperformstreamclone will print out a message if a stream clone was requested but couldn't happen for some reason. Removing this call ensures the message isn't printed twice.