doc: Enable Markdown doc compilation

[wenzeslaus]

The initial commit simply uncoments the Markdown compilation lines from #3849. This requires the actual Markdown files to be present, so this breaks the CI. This will stay like this for now. The PR is mean to be tested together with the Markdown files generated by script in #4620 (switch to this branch after generating the files).

Subsequent commits will add fixes of the compilation (missing tools, files, etc.).

To test this (assuming you already have the Markdown files):

Get virtual environment in some way (venv or pipenv).

Install dependencies:

pip install -r man/mkdocs/requirements.txt

Compile everything:

make distclean && ./configure ... && make
(cd man && make build-mkdocs)

[wenzeslaus]

This now builds Markdown files in dist based on the HTML-based .md files in the code (without a need to generate the files). make build-mkdocs (see above) can run as well.

[wenzeslaus]

When this is merged, ./utils/grass_html2md.sh can be easily tested in action with or without changes in #5054.

[petrasovaa]

Looking at the previous failure on Ubuntu:

fatal: destination path 'grass-addons' already exists and is not an empty directory.
ERROR: Failed to get addons files list from the Git repository </home/runner/.grass8/addons/grass-addons>.
fatal: Not a valid object name grass8

The tests run locally. @echoix , are these tests running in parallel perhaps?

[echoix]

I'm not sure I understand. Can you point me on what lines of a job log you're talking about ? It shouldn't appear on the main repo...

If it's the 4 Ubuntu jobs, no, it's not in parallel, it's pure gunittest.

[echoix]

It only runs in parallel if it's pytest, and you use the plugin pytest-xdist.

[cwhite911]

The docs are looking really good. I only had a few comments and suggest adding the following make command to man/Makefile for local testing.

serve-mkdocs:
	@cd $(MDDIR) ; SITE_NAME="GRASS GIS $(GRASS_VERSION_NUMBER) Reference Manual" \
	COPYRIGHT="© 2003-$(GRASS_VERSION_DATE) GRASS Development Team, GRASS GIS $(GRASS_VERSION_NUMBER) Reference Manual" \
	mkdocs serve

[cwhite911]

The topics page is functional, but we should improve the design in another PR.

[cwhite911]

Why remove r.mapcalc? I was having an issue building because the previous r.mapcalc dist wasn't getting removed with make distclean, so I needed to manually remove it.