doc: --recurse-submodules mostly applies to active submodules

The documentation refers to "initialized" or "populated" submodules, to explain which submodules are affected by '--recurse-submodules', but the real terminology here is 'active' submodules. Update the documentation accordingly. Some terminology: - Active is defined in gitsubmodules(7), it only involves the configuration variables 'submodule.active', 'submodule.<name>.active' and 'submodule.<name>.url'. The function submodule.c::is_submodule_active checks that a submodule is active. - Populated means that the submodule's working tree is present (and the gitfile correctly points to the submodule repository), i.e. either the superproject was cloned with ` --recurse-submodules`, or the user ran `git submodule update --init`, or `git submodule init [<path>]` and `git submodule update [<path>]` separately which populated the submodule working tree. This does not involve the 3 configuration variables above. - Initialized (at least in the context of the man pages involved in this patch) means both "populated" and "active" as defined above, i.e. what `git submodule update --init` does. The --recurse-submodules option mostly affects active submodules. An exception is `git fetch` where the option affects populated submodules. As a consequence, in `git pull --recurse-submodules` the fetch affects populated submodules, but the resulting working tree update only affects active submodules. In the documentation of `git-pull`, let's distinguish between the fetching part which affects populated submodules, and the updating of worktrees, which only affects active submodules. Signed-off-by: Damien Robert <damien.olivier.robert+git@gmail.com> Helped-by: Philippe Blain <levraiphilippeblain@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>