pull: move the cgresult logic in _pullchangeset Logical follow up of the previous changeset. The `_pullchangeset` is now responsible of setting the `pullop.cgresult`.

pull: move return code in the pull operation object With bundle2 we'll have multiple code path susceptible to be responsible for adding changeset during the pull. We move it to the pull operation to simplify this the coming logic. The one doing the adding the changegroup will set the value.

merge: use ancestor filename from planning phase instead of filectx ancestor test-merge-types.t changes a bit in flag merging. It relied on the implementation detail that 100% identical revlog entries are reused. The revlog reuse did that fctx.ancestor() saw an ancestor where there really not was one.

tests: prevent test-hup from hanging forever if the transaction does not start If the transaction fails to start because of some programing errors, the test would stay stuck in this while loop forever. We now added a basic safeguard that abort the loop if nothing happen in 10 seconds. 10 seconds sounds enough to let the server catch up and open a transaction.

revset: improve roots revset performance Previously we would iterate over every item in the subset, checking if it was in the provided args. This often meant iterating over every rev in the repo. Now we iterate over the args provided, checking if they exist in the subset. On a large repo this brings setting phase boundaries (which use this revset roots(X:: - X::Y)) down from 0.8 seconds to 0.4 seconds. The "roots((tip~100::) - (tip~100::tip))" revset in revsetbenchmarks shows it going from 0.12s to 0.10s, so we should be able to catch regressions here in the future. This actually introduces a regression in 'roots(all())' (0.2s to 0.26s) since we're now using spansets, which are slightly slower to do containment checks on. I believe this trade off is worth it, since it makes the revset O(number of args) instead of O(size of repo).

revset: improve _descendants performance Previously revset._descendants would iterate over the entire subset (which is often the entire repo) and test if each rev was in the descendants list. This is really slow on large repos (3+ seconds). Now we iterate over the descendants and test if they're in the subset. This affects advancing and retracting the phase boundary (3.5 seconds down to 0.8 seconds, which is even faster than it was in 2.9). Also affects commands that move the phase boundary (commit and rebase, presumably). The new revsetbenchmark indicates an improvement from 0.2 to 0.12 seconds. So future revset changes should be able to notice regressions. I removed a bad test. It was recently added and tested '1:: and reverse(all())', which has an amibiguous output direction. Previously it printed in reverse order, because we iterated over the subset (the reverse part). Now it prints in normal order because we iterate over the 1:: . Since the revset itself doesn't imply an order, I removed the test.

revsetbenchmark: remove python 2.7 dependency revsetbenchmark.py used check_output which only exists in python 2.7. This fixes it.

bundle2: read the whole bundle from stream on abort When the bundle processing abort on unknown mandatory parts, we now makes sure all the bundle content is read. This avoid leaving the communication channel in an unrecoverable state.

bundle2: add some distinction between mandatory and advisory part Mandatory part cannot be ignored when unknown. We raise a simple KeyError exception when this happen. This is very early version of this logic, see inline comment for future improvement lead.

bundle2: introduce a `parthandler` decorator Simple syntax sugar to register an handler for a new part type.