bundle2: no longer use 'retractboundary' in updatephases The new 'phase-heads' forced all added node to secret before advancing the boundary to work around the fact changesets were added as draft by default. This is no longer necessary since the changegroup part can now use the 'targetphase' parameter. Not doing this retract boundary call has a couple of advantages: * This makes implementing phases change tracking in the transaction much simpler since retract boundary can become a rare case. * Bundling secret changesets is not the norm. Exchange never does that and even for strip, the use-case is not common.Skipping the retract boundary will avoid useless work here. * Sending phase update on push can be simplified since we can rely on the behavior of 'cg.apply' for most of it. This means less phases update send for example. * We no longer needs to track and use the addednodes during unbundling. This make it possible to have multiple 'changegroup' and 'phase-heads' parts in the same bundle without them interfering with each others. The new part has not been part of any release yet so we do not offer backward compatibility yet. It is important to update this semantic before the 4.3 freeze happens.

bundle2: automatically add 'targetphase' parameter in writenewbundle If we are bundling secret changeset and the bundle will contain phase, we request the changegroup to be applied as secret. It will be useful for next patch as we are now sure that secrets changesets are applied as secret and not applied as draft then forced to secret.

bundle2: support the 'targetphase' parameter for the changegroup part By default unbundled changesets are drafts. We want to reduce the number of phases changes during unbundling by giving the possibility to the bundle to indicate the phase of unbundled changesets. The longer terms goal is to add phase movement tracking in tr.changes and the 'retractboundary' call is making it more complicated than we want.

changegroup: stop treating strip as special when dealing with phases Since 8e3021fd1a44, the strip bundle includes the phases of the stripping node. Hence we don't need this special case anymore. Dropping it will helps make the phase behavior more consistent across all exchanges medium.

match: inverse _anypats(), making it _prefix()

amend: new extension providing the amend command Various third parties have implemented the `amend` command, which is in high demand. This patch adds it as an experimental extension so its interface could be formalized in core directly. Since `commit --amend` is basically what `amend` should do. The command is just a thin wrapper around `commit --amend` and just prevent the editor from popping up by passing `--message`.