Defaults for options

[pdobsan]

May I suggest a small improvement both of the various documentations and of the help messages provided by stack on the command line. There are many flags/config options of the form --something/--no-something. It would be nice to always indicate which one is the default.

Or in the case when such a choice is dependent of other factors, try to give some explanation.

[chrisdone]

I think if we mirror the library-profiling output, via the boolFlags combinator we get a good result:

Example:

libProfiling =
  boolFlags False
            "library-profiling"
            "library profiling for TARGETs and all its dependencies"
            idm

=>

  --library-profiling      Enable library profiling for TARGETs and all its
                           dependencies (--no-library-profiling to disable)

Although this is only on master, if you have an older release it shows two separate flags.

[chrisdone]

Although probably some text from boolFlags to say "disabled by default" would enhance that message.

[pdobsan]

Combining the help messages for the alternatives is good.
Even the no-XYZ explanation could be spared if the --no-XYZ is consistently used everywhere. So that could be explained only once in general terms.
Hmm, maybe shorting the flag description is not so simple if the default is no-XYZ.

For any case, as you also note, defaults should be made clear.

[snoyberg]

Added in #4653