resolve: organize 'if confirm' conditionals Differential Revision: https://phab.mercurial-scm.org/D4123

index: pass only nodetree to nt_new() The function now only depends on the nodetree, not the index. Differential Revision: https://phab.mercurial-scm.org/D4111

index: drop now-redundant "nt" prefix of fields in nodetree struct Differential Revision: https://phab.mercurial-scm.org/D4110

index: move more fields onto nodetree type The fields moves are the ones that are not related to how the nodetree is used in the index and that will make sense for the new nodetree instance for a subset of the index that I'll add later. Differential Revision: https://phab.mercurial-scm.org/D4109

index: extract a type for the nodetree This is a first step towards exposing the nodetree as a Python type. Differential Revision: https://phab.mercurial-scm.org/D4108

index: make "nt_*" functions work on an initialized nodetree I want to be able to reuse these functions with another nodetree instance later (for disambiguating node prefix within a revset). That other nodetree instance won't want to be fully populated from the index, so this commit moves that part to the callers. Differential Revision: https://phab.mercurial-scm.org/D4107

changegroup: inline _packellipsischangegroup It now does nothing special. The logic is simple enough to inline in the 2 callers in narrow that need it. The changegroup generation APIs could probably be a bit simpler. But that's for another time. Differential Revision: https://phab.mercurial-scm.org/D4092