cmdutil: allow extra properties to be added to each context The changeset displayer allows setting extra keywords to be available to the templating layer. This patch adds an argument to displaygraph() to pass a dict of extra properties to be available to every changeset. Differential Revision: https://phab.mercurial-scm.org/D555

dirstate: perform transactions with _map using single call, where possible This is in the same style as https://phab.mercurial-scm.org/D493. In general, this replaces patterns such as: ``` f in self._map: entry = self._map[f] ``` with: ``` entry = self._map.get(f): if entry is not None: # use entry ``` Test Plan: `make tests` Differential Revision: https://phab.mercurial-scm.org/D663

extensions: register config item early Config items are likely to be used in during extensions setup. So we much register them before that. For example this apply to the 'win32text.warn' options.

extensions: factor extra data loading out Some of the extra data need to be registered earlier than they currently are (eg: config items). We first factor out the logic to registered them in a small function before reusing it in the next changeset.

configitems: register the 'win32text.warn' config

configitems: register the 'mq.secret' config

configitems: register the 'mq.plain' config

configitems: register the 'mq.keepchanges' config

configitems: register the 'mq.git' config

configitems: register the 'win32mbcs.encoding' config