Re: [RFC-PATCHv2] submodules: add a background story

> +STATES
> +------
> +
> +When working with submodules, you can think of them as in a state machine.
> +So each submodule can be in a different state, the following indicators are used:
> +
> +* the existence of the setting of 'submodule.<name>.url' in the
> +  superprojects configuration
> +* the existence of the submodules working tree within the
> +  working tree of the superproject
> +* the existence of the submodules git directory within the superprojects
> +  git directory at $GIT_DIR/modules/<name> or within the submodules working
> +  tree
> +
> +      State      URL config        working tree     git dir
> +      -----------------------------------------------------
> +      uninitialized    no               no           no
> +      initialized     yes               no           no
> +      populated       yes              yes          yes
> +      depopulated     yes               no          yes
> +      deinitialized    no               no          yes
> +      uninteresting    no              yes          yes
> +
> +      invalid          no              yes           no
> +      invalid         yes              yes           no
> +      -----------------------------------------------------
> +
> +The first six states can be reached by normal git usage, the latter two are
> +only shown for completeness to show all possible eight states with 3 binary
> +indicators. The states in detail:
> +
> +uninitialized::
> +The uninitialized state is the default state if no
> +'--recurse-submodules' / '--recursive'. An empty directory will be put in
> +the working tree as a place holder, such that you are reminded of the
> +existence of the submodule.
> +---
> +To transition into the initialized state
> +you can use 'git submodule init', which copies the presets from the
> +.gitmodules file into the config.
> +
> +initialized::
> +Users transitioned from the uninitialized state to this state via
> +'git submodule init', which preset the URL configuration. As these URLs
> +may not be desired in certain scenarios, this state allows to change the
> +URLs.  For example in a corporate environment you may want to run
> +
> +    sed -i s/example.org/$internal-mirror/ .git/config
> ++