debugdiscovery: add support for Json output They are some pre-output that will be impractical, I'll take care of it in the next changeset. Differential Revision: https://phab.mercurial-scm.org/D10223

perf-helper: add a new sampling revset based on anti-chain See inline documentation for details. Differential Revision: https://phab.mercurial-scm.org/D10222

perf-helper: add a small extension with revsets to select repository subset Playing with discovery requires building interesting case. To do this we need revsets to try to generate them. We start with a quite simple one. See documentation for details. Differential Revision: https://phab.mercurial-scm.org/D10221

amend: mark commit obsolete after moving working copy We were doing it this way: 1. move working copy (repo.setparents) 2. add obsmarkers (scmutil.cleanupnodes) 3. fix dirstate (dirstate.normal/drop) Step 1 and 3 are closely related, so let's move them together. It seems safest to create the obsmarkers last. This patch thus makes the order 1, 3, 2. Differential Revision: https://phab.mercurial-scm.org/D10197

pull: allow to specify multiple sources I end up needing that on a regular basis and it turn out to be very simple to implement. See documentation and test for details. Differential Revision: https://phab.mercurial-scm.org/D10159

pull: pre-indent a part of the function We are about to run it in a loop, so lets pre-indent it to clarify the actual change in the next changesets. Differential Revision: https://phab.mercurial-scm.org/D10158

command: clarify `postincoming` return and that return handling The command should return None or a return code. The previous code was returning boolean directly relying on the fact that `True → 1` and `False → 0`. This is a good road to troubles, so lets be explicit about that return. Differential Revision: https://phab.mercurial-scm.org/D10157