scheme: move the drive letter checking in its own function This help the readability of the main function as is was taking much more room than the main logic.

peer-or-repo: split the scheme between repo and peer Some of the scheme will always produce a peer and some will always produce a repository. So lets use different mapping to reduce the ambiguity.

peer-or-repo: stop relying on AttributeError in `islocal` This will confused pytypes in a future changeset.

repo-or-peer: deprecate calling `islocal` on non-path object There object have a `.local()` method and should use it.

tests: add the missing space to test-hghave.t (issue6762) log() in run-tests.py add a space to the end of all messages that it prints, and I missed this fact in my previous patch.

share: stop using 'islocal' with repo instance Having this level of polymorphism of the `islocal` function is weird, and we already have a way to know if the repo is local from the object itself. We are about to deprecate passing a non-bytes object to `islocal`, so clean this up beforehand. We might want to clean up this function too in the future, however this is another adventure.

peer-or-repo: make sure object in "scheme" have a `instance` object The previous form of having heterogeneous object in the dictionnary makes things more complicated than they needed to be. I am not super happy about the current (especially around 'islocal', that most item do not have), but this is already much better.

peer-or-repo: move the object setup in its own function The `_peerorrepo` function is problematic, because it can build different types of object (repository and peer). This make it hard to adjust the arguments to the type of object we needs. So this patch start a series of change to create peer and repo without going through a common function. We move the part of the function doing object setup it its own function to make it simpler to reuse in others contexts.

delta-find: use a single snapshot cache when applying a group to an object This will avoid walking the revlog over and over again in some situations. The difference is hard to show in our current benchmark suite, as the gain is lower than their overall instability.

delta-find: make sure we only use newer full snapshot as candidate The current code does not needs to protect against this, as there are no older snapshot in the current cache. However as we are getting ready to reuse this cache from one revision to another, we need the code to protect itself about what's coming.

delta-find: use sets instead of list in the snapshot cache This seems more appropriate.

delta-find: use a smarter object for snapshot caching This open the way for a longer lived cache.

find-delta: pass the cache-delta usage policy alongside the cache-delta The idea is to give higher level code more control to what will happens with the cache delta passed. This should help with controling how we treat delta's from different sources. The final goal of this change is to allow for server modes where the client can blindly accept any server delta without regards to any local constraints. This will be implemented in later changesets.

find-delta: move most of the debug-find-delta code in the debug module Lets us that module more. It will help us to keep revlog implementation details close to each other.

find-delta: minor preparatory change We are about to add more item in the cachedelta object, so lets access the item by index instead of doing a full extensions.

find-delta: rename _isgooddeltainfo Lets move to a more readable name now that we are allowed to. This cannot hurt.

test-revlog-raw: drop the overwrite of dead code The revlog class no longer have a _isgooddeltainfo method for a long time. So overwriting it does not get us anything. The test have been wrapping the right code since then anyway.

emitrevision: consider ancestors revision to emit as available base This should make more delta base valid. This notably affects: * case where we skipped some parent with empty delta to directly delta against an ancestors * case where an intermediate snapshots is stored. This change means we could sent largish intermediate snapshots over the wire. However this is actually a sub goal here. Sending snapshots over the wire means the client have a high odd of simply storing the pre-computed delta instead of doing a lengthy process that will… end up doing the same intermediate snapshot. In addition the overall size of snapshot (or any level) is "only" some or the overall delta size. (0.17% for my mercurial clone, 20% for my clone of Mozilla try). So Sending them other the wire is unlikely to change large impact on the bandwidth used. If we decide that minimising the bandwidth is an explicit goal, we should introduce new logic to filter-out snapshot as delta. The current code has no notion explicite of snapshot so far, they just tended to fall into the wobbly filtering options. In some cases, this patch can yield large improvement to the bundling time: ### data-env-vars.name = mozilla-try-2019-02-18-zstd-sparse-revlog # benchmark.name = perf-bundle # benchmark.variants.revs = last-100000 before: 68.787066 seconds after: 47.552677 seconds (-30.87%) That translate to large improvement to the pull time : ### data-env-vars.name = mozilla-try-2019-02-18-zstd-sparse-revlog # benchmark.name = pull # benchmark.variants.issue6528 = disabled # benchmark.variants.revs = last-100000 before: 142.186625 seconds after: 75.897745 seconds (-46.62%) No significant negative impact have been observed.

sqlitestore: add an `ancestors` method We will need it during bundling. The implementation mirror the one in revlog.

emitrevision: if we need to compute a delta on the fly, try p1 or p2 first Falling back to `prev` does not yield any real value on modern storage and result in pathological changes to be created on the other side. Doing a delta against a parent will likely be smaller (helping the network) and will be safer to apply on the client (helping future pulls by Triggering intermediate snapshop where they will be needed by later deltas).

emitrevision: simplify the fallback to computed delta Not using the stored delta, or having a full snapshot on disk behave the same ways, so lets use the same code path for that, this is simpler, and it update will be simpler.

emitrevision: also check the parents in the availability closure One of the point of having a closure is to gather the logic in it. So we gather the logic. The `parents[:]` part is a bit ugly but will be replaced by better code soon anyway.

emitrevision: add a small closure to check if a base is usable We will make more use of this and make it more complex too.

reuse-delta-base: improves some documentation The current code got me a bit confused initially. So a bit more documentation around it cannot hurt.