docs: add description about our code structure

Document most important directories when trying to understand our
project.

Signed-off-by: Paul Holzinger <[email protected]>

Author: Luap99

docs/CODE_STRUCTURE.md

@@ -0,0 +1,83 @@
+# Podman Codebase structure
+
+Description about important directories in our repository.
+
+### cmd/
+
+ - each directory here builds its own binary
+
+#### cmd/podman/
+
+- podman cli code, cli commands and flags are defined here, we are using github.com/spf13/cobra as library for command line parsing
+
+#### cmd/quadlet/
+
+- quadlet cli
+
+
+### docs/
+
+- sphinx based documentation for podman that is build on readthedocs (docs.podman.io)
+
+#### docs/source/markdown/
+
+- man pages for each podman command
+
+### libpod/ (only works on linux and freebsd)
+- underlying core for most podman operations, defines container, pod, volume management opartions
+- contains the database to store these informations on disk, either sqlite or botldb (our old db format)
+- integrates with our other libraries such as:
+	- containers/storage create and mount container storage
+	- containers/buildah for building images
+	- containers/common/libnetwork for network management
+
+### pkg/
+
+- various packages to do all sorts of different things
+
+#### pkg/api/
+
+- the HTTP REST API server code
+
+#### pkg/bindings/
+
+- the HTTP REST API client code
+- this package must have a stable API as it is for use by external consumers as well
+
+#### pkg/domain/
+
+- "glue" code between cli and the actual operations performed
+
+##### pkg/domain/entities/
+
+- the package defines two interfaces (ContainerEngine, ImageEngine) that more or less have a function for each cli command defined
+- it also defines a lot of types (structs) for the varoius options the functions accept
+
+##### pkg/domain/infra/tunnel/
+
+- implements the two interfaces for the remote mode (podman-remote) which just maps each operations to the bindings code from pkg/bindings which then talks to the remote server
+
+##### pkg/domain/infra/abi/
+
+- implements the two interfaces for the local mode (podman) that calls then directly into the core parts of libpod/ or our other libraries containers/{commmon,image,storage}...
+
+#### pkg/libartifact/
+
+- core code for the new podman artifact commands
+
+#### pkg/machine/
+
+- core code for podman machine commands
+
+### test/
+
+- Various tests suites, see the test [README.md](../test/README.md) for more details.
+
+#### vendor/
+
+- directory created with "go mod vendor"
+- this includes all go deps in our repo, DO NOT edit this directory directly, changes in dependencies must be made in their respective upstream repositories and then updated in go.mod
+
+#### bin/
+
+- build binaries are put here (bin/podman, bin/podman-remote, etc...)