D210: pushvars: move fb extension pushvars to core

[akushner (Aaron Kushner)]

akushner added inline comments.

INLINE COMMENTS

> commands.py:4012
> +    The --pushvars option is used to passed environment variables to server. If
> +    you want to disable this on your server for security purposes, you can add
> +    the following to your configuration file:

The --pushvars option sends strings to the server that become environment variables prepended with HG_USERVAR_. For example, '--pushvars ENABLE_FEATURE=true', provides the server side hooks with 'HG_USERVAR_ENABLE_FEATURE=true' as part of their environment.
  
  Pushvars can provide for user-overridable hooks as well as set debug levels. One example is having a hook that blocks commits containing conflict markers, but enables the user to override the hook if the file is using conflict markers for testing purposes or the file format has strings that look like conflict markers.
  
  To enable this feature on your server, add the following to your configuration file:
  
  [push]
  pushvars.server = true

REPOSITORY
  rHG Mercurial

REVISION DETAIL
  https://phab.mercurial-scm.org/D210

To: pulkit, #hg-reviewers
Cc: durin42, akushner, mercurial-devel