README

debuginstall: add Python information to debuginstall output (issue4128)

This change adds to the output of "hg debuginstall" information about the
Python being used by Mercurial.  It adds both the path to the Python
executable (i.e. the value of sys.executable) and the version of Python
(specifically the major, minor, and micro versions).

Below is an example of what the output looks like after this change.
The marked lines are the new output lines:

    $ hg debuginstall
    checking encoding (UTF-8)...
 -->showing Python executable (/Users/chris/.virtualenvs/default/bin/python)
 -->showing Python version (2.7.6)
    checking Python lib (/Users/chris/.virtualenvs/default/lib/python2.7)...
    checking installed modules (/Users/chris/mercurial)...
    checking templates (/Users/chris/mercurial/templates)...
    checking commit editor...
    checking username...
    no problems detected

Note that we use the word "showing" without an ellipsis for the new lines
because, unlike the other lines (except for "Python lib" which will be
adjusted in a subsequent commit), no check follows the display of this
information.

Mercurial
=========

Mercurial is a fast, easy to use, distributed revision control tool
for software developers.

Basic install:

 $ make            # see install targets
 $ make install    # do a system-wide install
 $ hg debuginstall # sanity-check setup
 $ hg              # see help

Running without installing:

 $ make local      # build for inplace usage
 $ ./hg --version  # should show the latest version

See http://mercurial.selenic.com/ for detailed installation
instructions, platform-specific notes, and Mercurial user information.