Improve Markdown code blocks & start moving docs to Markdown style (#19954)

- add additional parameters parsing (other implementations will just
  ignore them). E.g. if in RST we have:

  .. code:: nim
     :test: "nim c $1"

     ...

  then in Markdown that will be:

  ```nim test="nim c $1"
  ...
  ```

- implement Markdown interpretation of additional indentation which is
  less than 4 spaces (>=4 spaces is a code block but it's not
implemented yet). RST interpretes it as quoted block, for Markdown it's
just normal paragraphs.
- add separate `md2html` and `md2tex` commands. This is to separate
  Markdown behavior in cases when it diverges w.r.t. RST significantly —
most conspicously like in the case of additional indentation above, and
also currently the contradicting inline rule of Markdown is also turned
on only in `md2html` and `md2tex`. **Rationale:** mixing Markdown and
RST arbitrarily is a way to nowhere, we need to provide a way to fix the
particular behavior. Note that still all commands have **both** Markdown
and RST features **enabled**. In this PR `*.nim` files can be processed
only in Markdown mode, while `md2html` is for `*.md` files and
`rst2html` for `*.rst` files.
- rename `*.rst` files to `.*md` as our current default behavior is
  already Markdown-ish
- convert code blocks in `docgen.rst` to Markdown style as an example.
  Other code blocks will be converted in the follow-up PRs
- fix indentation inside Markdown code blocks — additional indentation
  is preserved there
- allow more than 3 backticks open/close blocks (tildas \~ are still not
  allowed to avoid conflict with RST adornment headings) see also
https://github.com/nim-lang/RFCs/issues/355
- better error messages
- (other) fix a bug that admonitions cannot be used in sandbox mode; fix
  annoying warning on line 2711

1 files changed, 77 insertions, 0 deletions

diff --git a/doc/packaging.md b/doc/packaging.md
new file mode 100644
index 000000000..7976dfe92
--- /dev/null
+++ b/doc/packaging.md
@@ -0,0 +1,77 @@
+=============
+Packaging Nim
+=============
+
+This page provide hints on distributing Nim using OS packages.
+
+See `distros <distros.html>`_ for tools to detect Linux distribution at runtime.
+
+See `here <intern.html#bootstrapping-the-compiler-reproducible-builds>`_ for how to
+compile reproducible builds.
+
+Supported architectures
+-----------------------
+
+Nim runs on a wide variety of platforms. Support on amd64 and i386 is tested regularly, while less popular platforms are tested by the community.
+
+- amd64
+- arm64 (aka aarch64)
+- armel
+- armhf
+- i386
+- m68k
+- mips64el
+- mipsel
+- powerpc
+- ppc64
+- ppc64el (aka ppc64le)
+- riscv64
+
+The following platforms are seldomly tested:
+
+- alpha
+- hppa
+- ia64
+- mips
+- s390x
+- sparc64
+
+Packaging for Linux
+-------------------
+
+See https://github.com/nim-lang/Nim/labels/Installation for installation-related bugs.
+
+Build Nim from the released tarball at https://nim-lang.org/install_unix.html
+It is different from the GitHub sources as it contains Nimble, C sources & other tools.
+
+The Debian package ships bash and ksh completion and manpages that can be reused.
+
+Hints on the build process:
+
+.. code:: cmd
+
+   # build from C sources and then using koch
+   make -j   # supports parallel build
+   # alternatively: ./build.sh --os $os_type --cpu $cpu_arch
+   ./bin/nim c -d:release koch
+   ./koch boot -d:release
+
+   # optionally generate docs into doc/html
+   ./koch docs
+
+   ./koch tools
+
+   # extract files to be really installed
+   ./install.sh <tempdir>
+
+   # also include the tools
+   for fn in nimble nimsuggest nimgrep; do cp ./bin/$fn <tempdir>/nim/bin/; done
+
+What to install:
+
+- The expected stdlib location is /usr/lib/nim
+- Global configuration files under /etc/nim
+- Optionally: manpages, documentation, shell completion
+- When installing documentation, .idx files are not required
+- The "compiler" directory contains compiler sources and should not be part of the compiler binary package
+