RFE: fmf plugin/dialect

[LecrisUT]

Description

Right now there is only one "dialect" of the fmf files being tmt test files, while if we want to use fmf in other context, they would have an ambiguity if a fmf tree is supposed to be processed by tmt or another program. An example of this is tmt lint.

Proposal

Define a standard .fmf/plugins file which would be read as a requirements.txt file, e.g.

# .fmf/plugins
tmt
tmt-cmake @ git+https://github.com/LecrisUT/tmt-cmake@main

Fmf responsibility here would be just to:

• Check that the plugin requirements are satisfied
  • name and specifier
  • maybe extras and marker
  • ignore url
• Print out a requirements.txt of the unsatisfied plugins when executing cli
• Print out all the .fmf/plugins as is (in case this will evolve later). Useful if the user would want to always install the plugins

Impact in tmt/testing-farm

• tmt would have to suggest adding a .fmf/plugins file with tmt line
• testing-farm would check the .fmf/plugins and if there is a package there that it does not recognize with python3dist() as pre-installed, then fail early