D1440: docs: add args/returns docs for some cmdutil, context, and registrar functions

[pulkit (Pulkit Goyal)]

pulkit added a comment.


  I see you used the word `string` at few places, do you mean the Python string? If yes, that won't be true on Python 3 as most of the things are bytes.

REPOSITORY
  rHG Mercurial

REVISION DETAIL
  https://phab.mercurial-scm.org/D1440

To: rlevasseur, #hg-reviewers, lothiraldan
Cc: pulkit, lothiraldan, mercurial-devel