Turns out this was not a good idea as it would too easy to trigger.
If a saturnin sub-command was called from within itself (or another other
sub-command), the $SATURNIN_CONF_PATH computed earlier would just double,
leading to unwanted behavior of saturnin__conf_find(), which would find
items twice.

The original problem should be adressed another way; the testing case
be covered by either writing tests on a lower level; eg. unit tests
and use saturnin__conf_find() or saturnin__conf() without forking.

Another solution on part of Saturnin could be to introduce different
variable (e.g. SATURNIN_CONF_DIRS) for values computed by launcher
and keep $SATURNIN_CONF_PATH just for user.

Overview of changes:

 *  Made saturnin__mkpath() respect $SATURNIN_CONF_PATH

    Ignoring the environment variable would make it hard to do system
    tests in staged environments (such as RPM's `%check`) that would
    rely on saturnin__conf().

This allows prepending config locations to Saturnin.  This should be
normally used only in cases of staged installattions, such as in sanity
tests.

Overview of changes:

 *  Added --saturnin-get-subcommands devel key

    In last update I inanely removed _ls_sc sub-command used by
    completion example in saturnin-demo.  This is a final replacement,
    which is actually consistent with the rest of plumbing commands.

 *  Improved docstrings for sfdoc

    Added and fixed some old docstrings as well as added module
    docstring.

 *  Improved usage errors with newer Shellfu's pretty.sh interface

    pretty.sh in newer Shellfu can handle usage messages in more
    user-friendly way, by providing option to append error reason
    to the message itself.

    (With previous version, one could achieve similar effect but with
    more negative effect on readability.)

 *  Fixed build-time test for Debian

    Turns out that dehbelper does not install the package on its own so
    we have to deal with it manually.

 *  Minor code cleanup

A less intrusive replacement for _ls_sc subcommand

Overview of changes:

 *  Fixed many packaging errors

    Added proper (build) dependencies, fixed build-time tests (rpm and
    deb), updated meta-data.

 *  Updated code to work with for Shellfu v0.10.0

 *  Removed obsolete internal subcommands

 *  Added support for -V for version (SemVer-formatted)

 *  Changed license to LGPLv2

Overview of changes:

 *  Added option to enable stronger debugging

    You can use PRETTY_DEBUG_EXCLUDE to mute some output from your apps
    that might not be always relevant (example launcher in saturnin-demo
    does this).  This option re-sets the variable to empty string, making
    sure your pretty apps will show as much as possible.

 *  Added tests to deb and rpm packages

 *  Added test header (requires Shellfu v0.9.7+)

 *  Fixed, tidied up and updated project and packaging meta-data

 *  Fixed usage test

 *  Codebase maintenance

$0 is not changed by functions so this could not have worked (strange it
*did* work on Fedora, I still have to find out why).

Overview of changes:

 *  Enabled adding meta command help text

    User can now specify SATURNIN_META_HELP environment variable to
    control what happens when meta-command is called with `--help`
    argument.

 *  Removed `conf` from default sub-command list

    The command is essentially internal; usage from outside is possible
    but requires knowledge normally only available to developers.

New variable SATURNIN_META_HELP can be used to control what happens when
user calls the meta command with `--help` argument.

conf is Saturnin's internal command to access common configuration.  It
could be, in theory, useful for end-user to investigate the configuration,
but they would already need to know how it works and which configuration
keypaths or sections they want to look at.

Bettter hide it; it's not worth for the potential confusion.

Note that the command could actually even be removed one day since
internally it's much more efficient to use saturnin__conf().

Overview of changes:

 *  Properly filter subcommands on listing

    In contexts like main --help and tab completion, Saturnin would show
    also arbitrary files from libexec that did not start with dedicated
    prefix ($SATURNIN_LIBEXEC_PREFIX).  This was a mistake and was never
    intended to work that way.

 *  Hook code is now run as separate bash process

    Running it within sub-command code was a little bit too unsafe;
    there's no need to be evil^Weval here.

 *  Rewrote saturnin__version() (used for app --version)

    Newly, --version will only incorporate tagline if it was defined in
    mkit.ini.

    Also "Powered by Saturnin" line has been added so that we don't have
    to ask user every time.

 *  Added --saturnin-get-saturnin-version

    It's a good idea to include this with test reports and the like so
    we're making it more accessible to scripts.

 *  API documentation clarifications

 *  Codebase maintenance

 *  Refactoring for code readability

Only print tagline if defined (similar to codename); do not make it up
with silly string.

Also we can do away without any local variables *and* very safely inside
79 character width recommendation.

eval was little bit too much.

This was always intended; sub-commands starting with dedicated prefix
is the mandatory convention.

As recommended by Shaturnin style guide:

    https://github.com/AloisMahdal/shellfu/blob/master/notes/style.md

As recommended by Shellfu style:

    https://github.com/AloisMahdal/shellfu/blob/master/notes/style.md

Overview of changes:

 *  Added generic config file finder

    This can be used to find config files other than INIs but using the
    same merging mechanism.  For example, `saturnin__conf_find "foo"`
    should output to first existing instance of file "foo", which could
    live under any of paths set in SATURNIN_CONF_PATH (typically
    /usr/share/app/ini.d/dist/foo, /etc/app/foo, ~/.config/app/foo,
    ~/.config/app/ini.d/my/foo...).

    This function is now also internally usef by saturnin__conf().

 *  Added module-version meta-data for future Shellfu generations

    Current version of Shellfu does not support this yet, but in future
    it should read this and display in lists, man pages, etc.