[PATCH v2] pager: migrate heavily-used extension into core

[Augie Fackler]

> On Feb 6, 2017, at 19:26, Jun Wu <quark at fb.com> wrote:
> 
>> As a sketch of where this is headed, API-wise:
>> 
>> class ui:
>> def pager(self, command, category):
> 
> Just to confirm if I understand correctly, command and category are only
> used to find out the actual pager command from the config? That looks good.
> Maybe swap category and command and make command (or both) optional, to
> discourage using commands in configs.

I couldn't quite wrap my head around categories in the end. The categories I could sort of see are:

cat:
  cat, annotate, grep
status:
  status, summary, resolve
log:
  log, tags, incoming, outgoing
diff:
  export, {log, incoming, outgoing with --patch}, qdiff
???:
  files, manifest, locate, help

For now, the series discards the notion of a category in the 10th patch or so, but we can easily re-add it or make it the preferred option if we can figure out what the ontology is here.

If you want to see the work in progress stack, it's here: https://hg.durin42.com/hg-wip/log?rev=%40%3A%3A7c0170f0420f%20-%20%40&revcount=50