[WIP] Download section

Signed-off-by: Cristian Le <[email protected]>

docs/guides/user/download.md

@@ -0,0 +1,73 @@
+# Downloading the project
+
+First step is where do we even get the files we need to start using the project.
+As you're probably aware by now, C/C++ projects do not have a concise packaging
+system [^1][^2] like [PyPI] is for python, so the starting point here is not that
+straight-forward. The actual project that implemented this template should
+document where they are officially packaging the project, usually on the
+front-page of their git repository or documentation.
+
+Regardless, here I will try to cover some of the common sources and conventions
+where you can find the project.
+
+[PyPI]: https://pypi.org/
+
+---
+
+## Where do I download the project from?
+::::{tab-set}
+:::{tab-item} As an end-user
+For the most part you should look for a [packaged] source, even the project you
+want to use is a library that you would be using in your own C/C++ project.
+
+When importing the project within another CMake project, the recommended way is
+[using `FetchContent`], which will internally use either the [packaged] or
+[source] version.
+:::
+:::{tab-item} As an upstream developer
+You are primarily interested in the [source] version. When working on multiple
+projects, it is especially useful to know how to setup your [CMakeUserPreset] so
+that you can easily switch between one project and another.
+:::
+:::{tab-item} As a downstream packager
+You should be aware on how get the project from [source]. The original git
+source is preferred since CMake does not bundle any additional metadata in its
+archive.
+:::
+::::
+
+## Packaged version
+
+Usually you will find the project
+
+## Source project
+
+## Using `FetchContent`
+
+## Other build-system
+
+Good luck, you have reached the wild-west. You are mostly on your own now.
+
+Some projects can have other ways of importing the project using [`pkgconf`],
+however, for consuming CMake projects, it is greatly discouraged to rely on
+these because it cannot contain the same amount of metadata, e.g. for
+[c++ modules], it does not contain the compiler used for packaged compiled
+library, that would tell the consumer if they need to re-compile the project or
+not, but on the other-hand, such information is used when consuming CMake's
+[`find_package`].
+
+[packaged]: #packaged-version
+[source]: #source-project
+[using `FetchContent`]: #using-fetchcontent
+[`pkgconf`]: https://github.com/pkgconf/pkgconf
+[c++ modules]: https://en.cppreference.com/w/cpp/language/modules
+
+[CMakeUserPreset]: TBD
+
+[`find_package`]: inv:cmake:cmake:command#command:find_package
+
+[^1]: There is a proposal within CMake to at least unify the dependency backend
+      [^2] which would be a pre-requisite for having a unified packaging system
+      using CMake. But still it is a long way until there can be a `pip`-like
+      interface to install projects.
+[^2]: <https://gitlab.kitware.com/cmake/cmake/-/issues/22686>

docs/guides/user/index.md

@@ -8,6 +8,7 @@ hidden: true
 glob: true
 ---
 who-is-the-user
+download
 ```
 
 This is a general guide for how a user can interact with modern CMake project