merge.applyupdates: call driverconclude after performing merge actions This will be a chance for the merge driver to finish resolving or generating any driver-resolved files. As before, having a separate error state from 'unresolved' is too big a refactoring for now, so we hack around it by setting unresolved to a positive value when necessary.

merge.applyupdates: call driverpreprocess before starting merge actions We also need to update our internal state to whatever state driverpreprocess leaves it in. Adding an error state separate from the unresolved count is too big a refactoring for now, so we hack around it by setting it to a positive value to indicate an error state.

merge: add stubs for preprocess and conclude steps of merge driver The exact semantics for what should happen (particularly with respect to error handling) are still a bit hard to pin down, so I think it's better to experiment with it as an extension for now. For now this stub will act as a convenient point for extensions to hook on.

commands.resolve: don't allow users to mark or unmark driver-resolved files Users will often be in the habit of running 'hg resolve --mark --all' after resolving merge conflicts in source files. We need to make sure this doesn't cause driver-resolved files to be marked. 'hg resolve --all' will resolve driver-resolved files, though. The weird conditional structure is to accommodate an upcoming patch.

resolve: only create wctx once This allows for status and other results on the wctx to be cached between iterations.

dirstate: fix invalid reference to self.ui

spelling: trivial spell checking