Single-source documentation where reasonable?

[abathur]

I don't know much about this and a few casual searches haven't turned up many obvious options. It smells like something I'll spin my wheels a lot on.

resholve is largely a solo effort so far, so I'm keeping documentation support fairly modest to avoid meta-work keeping multiple copies/variants in sync, or spinning my wheels on cobbling together a single-sourcing workflow.

Current docs are:

• The --help flag provides a terse overview of flags and their purpose. (I'm not super happy with ConfigArgParse's default help formatting, and keeping this reference terse mitigates my complaints with it).
• The manpage (currently hand-written in mdoc) is the only canonical reference.

If you have experience single-sourcing that directly applies or transfers to --help, manpage, README.md, and possibly an external site at some point, help bootstrapping the workflow/toolchain here would be much appreciated.

It's worth discussing the approach before diving in, but I think my main stipulation is that I don't want to single-source in a way that is crappy/suboptimal for all or most of the outputs (i.e., I don't want to just throw the manpage through a few tools to generate plaintext, html, and markdown).