doc/README

cmdutil: remove the redundant commit during amend

There was an extra commit made during the amend operation to track the
changes to the working copy. However, this logic was written a long time back
and newer API's make this extra commit redundant. Therefore, I am removing the
extra commit. After this change, I noticed that

  - Execution time of the cmdutil.amend improved by over 40%.
  - Execution time of "hg commit --amend" improved by over 20%.

Test Plan:
I ensured that the all the hg tests passed after the change. I had
to fix a few tests which were aware of the extra commit made during the amend.

Differential Revision: https://phab.mercurial-scm.org/D636

Mercurial's documentation is kept in reStructuredText format, which is
a simple plain text format that's easy to read and edit:

  http://docutils.sourceforge.net/rst.html

It's also convertible to a variety of other formats including standard
UNIX man page format and HTML. You'll need to install Docutils:

  http://docutils.sourceforge.net/

Use the Makefile in this directory to generate the man and HTML pages.