Mercurial provides a command-server which can be used with 'chg' binary.

This change allows to replace the 'hg' binary by a 'chg' binary for

usage in a custom script.
This speeds up a single post from 2,8 seconds to 1,1 seconds.

Use MercurialClient('chg') in our custom script and

saw that debugging output calls 'chg' instead of 'hg'.
Default MercurialClient() still uses 'hg' binary.