[boost] [program_options] behaviour change for implicit options

Subject: [boost] [program_options] behaviour change for implicit options
From: Vladimir Prus (vladimir.prus_at_[hidden])
Date: 2017-06-25 19:05:05

Hi,

I have committed, and merged to master, a change making program_option
consider subsequent tokens for values of implicit options.

For example, if "foo" is implicit option and "bar" is some other option,
then:

1. "--foo --bar" will be parsed as option "foo" followed by "bar", and 
implicit option for "foo" will be used.

2. "--foo bar" will be parsed as option "foo" with the value of "bar"

This is the way things worked prior to 1.59, was changed in 1.59, 
continued to cause confusion, and is now reverted back.

For background, see:

- http://permalink.gmane.org/gmane.comp.lib.boost.devel/269832
- https://github.com/boostorg/program_options/issues/25

Just in case client code might need to check this behaviour, I've added
a feature macro, BOOST_PROGRAM_OPTIONS_IMPLICIT_VALUE_NEXT_TOKEN, which
will be set to 1 starting with 1.65.

Thanks,
Volodya