MacPorts Base: Support for a lower level of debug output, like ui_trace, or ui_debug2/ui_debug3?

[Christopher Nielsen]

Take a look at the following comment in the open PR, which illustrates the before/after:

https://github.com/macports/macports-base/pull/243#issuecomment-851587566

> On 2021-06-02-W, at 16:52, Ryan Schmidt <ryandesign at macports.org> wrote:
> 
>> On May 26, 2021, at 08:38, Christopher Nielsen wrote:
>> 
>> I’m referring to debug output like the following, in this cases taken from one of our builtbot logs. Some of these are generated by base, while others are generated by the portgroups themselves.
>> 
>> While I’m not necessarily advocating that we hide all of these (via output at level debug2 or debug3), we’d have the option.
>> 
>> Does that make sense?
> 
> Not yet.
> 
>> DEBUG: Will append MACPORTS_LEGACY_SUPPORT_DISABLED=1 to extract.env
>> DEBUG: Will append MACPORTS_LEGACY_SUPPORT_DISABLED=1 to configure.env
>> DEBUG: Will append MACPORTS_LEGACY_SUPPORT_DISABLED=1 to build.env
>> DEBUG: Will append MACPORTS_LEGACY_SUPPORT_DISABLED=1 to destroot.env
>> DEBUG: Will append MACPORTS_LEGACY_SUPPORT_DISABLED=1 to test.env
> 
> Which of this output do you propose to change to different debug levels any why?
> 
> I don't know which of this output is generated by portgroups and which by base but I can guess that output like "Will append MACPORTS_LEGACY_SUPPORT_DISABLED=1 to extract.env" is generated by the legacysupport portgroup and I wonder why this output for example is needed at all when one can already see in later debug lines what extract.env gets set to.