deltafind: issue debug information when we fast-path rivial case too More debug options never hurts.

delta-find: gather the condition to blindly use a full snapshot together We are about to make the `if` body bigger, so having only one of them is simpler/

delta-find: initialize the debug information much sooner (when possible) This help us to record debug information in alternative path.

delta-find: fix `parents` round detection We should compare integer with integer, instead of bytes (node).

delta-find: intrduce a `_one_dbg_data` method This helps with the initialisation of the expected debug information.

delta-find: move final debug processing in a `_dbg_process_data` method This will help us making sure we can call the necessary debugging code in alternative codepath.

delta-fine: use the `_debug_search` attribute directly By adjusting the value at creation time, we can avoid the need to use and intermediate variable.

delta-find: move the `gather_debug` logic in a property This will make it simpler to get be reused in multiple places.

tests: check `pulled-delta-reuse-policy=forced` without general delta If general delta is not available, the amount of delta we can reuse at all will be more limited. We check that application still work and does not corrupt the repository.

tree-manifest: allow `debugupgraderepo` to run on tree manifest repo There does not seems to be anything wrong with running the current logic on them. So we remove the limitation.

bundles: clarify streaming v2 bundle usage This seems useful to clarify through the documentation (we were still using debugcreatestreamclonebundle, even though 'hg bundle' is already an option...).

stream-clone: update debugcreatestreamclonebundle helps People to stop using streamv1, so we should point them to alternative in the place where people might find it.

rewrite: simplify the `retained_extras` extra logic First, we move the definition of value outside of the rebase extensions, as this apply to all rebase-like operation and some live in other place (like evolve). Second we make it a simple set, so that it is easy for an extension to add a new value in it. Third, we move the associated logic in core too. That make it easily available to other extensions. Fourth we simplify it usage, as the verbose version of the filtering is just a handful on line long, we are just going to test all the value for updates, so the Projection overlay is not bringing much here. Note that, we make it a module level set, is a key is worth preserving it is probably worth preserving in all cases. This was already the behavior prior to this change.

revlog: fix a bug in revlog splitting Specifically, if the .i.s files are not added to the transaction, then a follow-up modification of such a file records it into transaction as non-empty, which is incorrect.

stream-clone: smoothly detect and handle a case were a revlog is split This detect and handle the most common case for a race condition around stream and revlog splitting. The one were the revlog is split between the initial collection of data and the time were we start considering stream that data. In such case, we repatch an inlined version of that revlog together when this happens. This is necessary as stream-v2 promised a specific number of bytes and a specific number of files to the client. In stream-v3, we will have the opportunity to just send a split revlog instead. Getting a better version of the protocol for stream-v3 is still useful, but it is no longer a blocket to fix that race condition. Note that another, rarer race condition exist, were the revlog is split while we creating the revlog and extracing content from it. This can be dealt with later.