Made Commands.md dynamically generated

[TheQwertiest]

Replaced docs/markdown/Commands.md with dynamic generation from template:

• Added a helper script tools/regenerate_docs.py:
  This script generates docs/markdown/Commands.md from docs/markdown_dynamic/Commands.md, using the current meson.py to get the relevant data. Template rendering is implemented via jinja2 Python package.
• Added a call to tools/regenerate_docs.py from docs/meson.build (which is used to generate site docs during release).
• Rewrote corresponding unit-test: now it only checks two things:
  • All commands are present (i.e. section names).
  • All commands have corresponding place-holders.

[TheQwertiest]

PS: I can rewrite the test properly if the jinja2 requirement can be satisfied somehow (e.g. install jinja2 on CI. The test can be optional so that users could run the whole test suite even if they don't have jinja on their machine).

[TheQwertiest]

Another option would be to make doc generation actually dynamic and move this script invocation to meson/docs/meson.build and template to docs/markdown (instead of a current fully-rendered Commands.md). This way there would be no need to test any options at all (only commands presence), since docs will always contain the up-to-date info. There won't be a need for user to manually invoke the script as well.

[TheQwertiest]

Added a test to enforce template usage: test checks if the markdown/Commands.md is consistent with templates/Commands.md

[TheQwertiest]

Rebased to resolve conflicts

[jpakkane]

Fully dynamic is better. Whenever something can be done so it works without manual labor, it should be done.

[TheQwertiest]

@jpakkane , done. But please check if it works on your machine as well, since site generation (and upload) is not covered by any tests (AFAIK).

[lgtm-com]

This pull request introduces 2 alerts when merging 68cf874 into d6c6b93 - view on LGTM.com

new alerts:

• 1 for Wrong name for an argument in a call
• 1 for Unused import

[jpakkane]

It currently fails because regenerate_docs.py does not have the executable bit set.

Testing it yourself is simple:

• Install hotdoc (most easily via pip)
• go in the docs subdir
• run ../meson.py . builddir && ninja -C builddir

[TheQwertiest]

Strange, it works for me :\
I'll add the flag anyway =)

[TheQwertiest]

Added a flag, renamed templates to markdown_dynamic (for better discoverability) and rebased for good measure :D