[gentoo-commits] proj/R_overlay:master commit in: doc/rst/

[André Erdmann]

commit:     0678580564dcf6aa8e2587d3b04d62544265ca74
Author:     André Erdmann <dywi <AT> mailerd <DOT> de>
AuthorDate: Wed Jun 26 17:28:39 2013 +0000
Commit:     André Erdmann <dywi <AT> mailerd <DOT> de>
CommitDate: Wed Jun 26 17:28:39 2013 +0000
URL:        http://git.overlays.gentoo.org/gitweb/?p=proj/R_overlay.git;a=commit;h=06785805

doc/rst: "run hooks", "distmap"

---
 doc/rst/usage.rst | 643 ++++++++++++++++++++++++++++++++----------------------
 1 file changed, 383 insertions(+), 260 deletions(-)

diff --git a/doc/rst/usage.rst b/doc/rst/usage.rst
index 078a7ac..2daedce 100644
--- a/doc/rst/usage.rst
+++ b/doc/rst/usage.rst
@@ -1010,6 +1010,22 @@ A local directory will never be modified.
    consider using one of the **websync** repo types, websync_repo_ and
    websync_pkglist_.
 
+---------
+ distmap
+---------
+
+*roverlay* uses a text file to store information about files in the package
+mirror directory (OVERLAY_DISTDIR_ROOT_). This is necessary for comparing
+package files from repos with files for which an ebuild has already been
+created (in previous runs).
+
+With the help of the *distmap file*, *roverlay* is able to determine whether
+upstream has changed a package file silently and creates a revision-bumped
+ebuild for the *new* package file.
+
+The *distmap file* can optionally be compressed (bzip2 or gzip), which
+reduces its size considerably.
+
 
 =====================
  Additions Directory
@@ -1790,6 +1806,354 @@ Moving such packages to a "R-package" sub directory would be possible, too:
    END;
 
 
+=============
+ Event Hooks
+=============
+
+*roverlay* is able to call a script when certain events occur, e.g. after
+successful overlay creation, which can be used to perform additional actions
+without touching *roverlay's* source code.
+
+To realize this, *roverlay* determines whether a given event is permitted
+(`event policy`_) and, if so, creates a `hook environment`_ and runs the
+script. Additionally, shell scripts can load *roverlay's* *$FUNCTIONS* file,
+which provides extra functionality.
+
+.. Note::
+
+   *roverlay* waits until the script terminates and thus possibly waits
+   forever.
+
+
+----------------------
+ Default event script
+----------------------
+
+The default event script (``mux.sh``) loads *$FUNCTIONS* and then runs the
+following script files (by sourcing them), in order:
+
+#. all files from ADDITIONS_DIR_/hooks/<event> that end with *.sh*
+   (``<ADDITIONS_DIR>/hooks/<event>/*.sh``)
+#. all files ADDITIONS_DIR_/hooks that end with *.<event>*
+   (``<ADDITIONS_DIR>/hooks/*.<event>``)
+
+So, there are two naming schemes for *hook scripts*.
+Either one is acceptable, but it is advised to stay consistent.
+Having the same script at both locations results in executing it twice.
+
+..  Note::
+
+   The default event script enables *nounset* behavior, which causes the
+   shell command interpreter to exit abnormally if an unset variable is
+   accessed.
+
+
+++++++++++++++++++++++++++
+ Activating a hook script
+++++++++++++++++++++++++++
+
+Activating a hook script can be done by symlinking it:
+
+..  code-block:: text
+
+   ln -s <real script> ${ADDITIONS_DIR}/hooks/<event>/<name>.sh
+   # or
+   ln -s <real script> ${ADDITIONS_DIR}/hooks/<name>.<event>
+
+
+++++++++++++++++++++++++++
+ Adding a new hook script
+++++++++++++++++++++++++++
+
+As hinted before, *hook scripts* are simple shell scripts. The following
+template gives an idea of how to write them:
+
+..  code-block:: sh
+
+   #!/bin/sh
+   #set -u
+
+   # load essential functions
+   # (not necessary when using the default event script)
+   . "${FUNCTIONS?}" || exit
+
+   ## load additional function files, if any
+   #$lf <name(s)>
+
+   # script body
+   #
+   # when redirecting output to $DEVNULL, use ">>" instead of ">" as
+   # $DEVNULL could be a file
+   #ls >>${DEVNULL}
+   #
+   # ...
+
+
+   # the script must not exit if everything went well (return is ok)
+   return 0
+
+
+--------------
+ Event Policy
+--------------
+
+The *event policy* controls whether a certain event actually triggers a script
+call or not.
+It is constructed by parsing the EVENT_HOOK_RESTRICT_ config option:
+
+* a word prefixed by ``-`` means *deny specific event* (-> blacklist)
+* the asterisk char ``*`` (or ``+*``) sets the policy to
+  *allow unless denied* (blacklist) or *allow all*
+* a word prefixed by ``+`` or without a prefix char means
+  *allow specific event* (-> whitelist)
+* the asterisk char with ``-`` as prefix (``-*``) sets the policy to
+  *deny unless allowed* (whitelist) or *deny all*
+
+
+The policy defaults to *allow all* if ``EVENT_HOOK_RESTRICT`` is not set in
+the config file. An empty string sets the policy to *deny all*.
+
+
+------------------
+ Hook Environment
+------------------
+
+.. table:: environment variables provided by *roverlay*
+
+   +----------------+-------------------+-----------------------------------------+
+   | variable       | source            | notes / description                     |
+   +================+===================+=========================================+
+   | PATH           | os.environ        |                                         |
+   +----------------+-------------------+-----------------------------------------+
+   | LOGNAME        | os.environ        |                                         |
+   +----------------+-------------------+-----------------------------------------+
+   | SHLVL          | os.environ        |                                         |
+   +----------------+-------------------+-----------------------------------------+
+   | TERM           | os.environ        |                                         |
+   +----------------+-------------------+-----------------------------------------+
+   | HOME           | os.environ        |                                         |
+   +----------------+-------------------+-----------------------------------------+
+   | ROVERLAY_PHASE | event             | event that caused the script to run     |
+   +----------------+-------------------+-----------------------------------------+
+   | OVERLAY        | config            | overlay directory (`OVERLAY_DIR`_),     |
+   +----------------+-------------------+ initial working directory               |
+   | S              | *$OVERLAY*        |                                         |
+   +----------------+-------------------+                                         |
+   | PWD            | *$OVERLAY*        |                                         |
+   +----------------+-------------------+-----------------------------------------+
+   | DISTROOT       | config            | package mirror directory                |
+   |                |                   | (`OVERLAY_DISTDIR_ROOT`_)               |
+   +----------------+-------------------+-----------------------------------------+
+   | TMPDIR         | os.environ,       | directory for temporary files           |
+   |                | *fallback*        |                                         |
+   +----------------+-------------------+                                         |
+   | T              | *$TMPDIR*         |                                         |
+   +----------------+-------------------+-----------------------------------------+
+   | ADDITIONS_DIR  | config            | directory with supplementary files      |
+   |                |                   | (`OVERLAY_ADDITIONS_DIR`_)              |
+   +----------------+-------------------+                                         |
+   | FILESDIR       | *$ADDITIONS_DIR*  |                                         |
+   +----------------+-------------------+-----------------------------------------+
+   | SHLIB          | *$ADDITIONS_DIR*, | A list of directories with shell        |
+   |                | *installed?*      | function files                          |
+   |                |                   | (optional, only set if any dir exists)  |
+   +----------------+-------------------+-----------------------------------------+
+   | FUNCTIONS      | *$ADDITIONS_DIR*, | file with essential shell functions     |
+   |                | *installed?*      | (optional, only set if it exists)       |
+   +----------------+-------------------+-----------------------------------------+
+   | DEBUG          | log level         | *shbool* (``y`` or ``n``) that          |
+   |                |                   | indicates whether debug messages should |
+   |                |                   | be printed                              |
+   +----------------+-------------------+-----------------------------------------+
+   | VERBOSE        | log level         | *shbool*                                |
+   +----------------+-------------------+-----------------------------------------+
+   | QUIET          | log level         | *shbool* that indicates whether scripts |
+   |                |                   | should be quiet                         |
+   +----------------+-------------------+-----------------------------------------+
+   | NO_COLOR       | *n/a*             | *shbool*. Always set to *y* since       |
+   |                |                   | colored output should not be produced   |
+   +----------------+-------------------+-----------------------------------------+
+   | NOSYNC         | config            | *shbool* that indicates whether data    |
+   |                |                   | transfers from/to remote machines is    |
+   |                |                   | allowed (NOSYNC_)                       |
+   +----------------+-------------------+-----------------------------------------+
+   | EBUILD         | config            | the *ebuild* executable                 |
+   +----------------+-------------------+-----------------------------------------+
+   | GIT_EDITOR     | *n/a*             | set to */bin/false*                     |
+   +----------------+-------------------+                                         |
+   | GIT_ASKPASS    | *n/a*             |                                         |
+   +----------------+-------------------+-----------------------------------------+
+
+
+The default *essential shell functions* file (*$FUNCTIONS*) makes,
+when included in the hook script, most of the enviroment variables readonly.
+
+
+.. table:: variables provided by *$FUNCTIONS*
+
+   +-----------------+-------------------------------------------------------+
+   | variable        | description                                           |
+   +=================+=======================================================+
+   | IFS_DEFAULT     | default *internal field separator*                    |
+   +-----------------+-------------------------------------------------------+
+   | IFS_NEWLINE     | *IFS* for iterating over text lines                   |
+   +-----------------+-------------------------------------------------------+
+   | DEVNULL         | */dev/null* target (could also be a file)             |
+   +-----------------+-------------------------------------------------------+
+   | EX_ERR          | default error exit code                               |
+   +-----------------+-------------------------------------------------------+
+   | EX_ARG_ERR      | default exit code for arg errors                      |
+   +-----------------+-------------------------------------------------------+
+   | SCRIPT_FILENAME | file name of the hook script                          |
+   +-----------------+-------------------------------------------------------+
+   | SCRIPT_NAME     | name of the hook script (without file extension)      |
+   +-----------------+-------------------------------------------------------+
+   | lf              | reference to a function that loads additional shell   |
+   |                 | function files                                        |
+   +-----------------+-------------------------------------------------------+
+
+
+*$FUNCTIONS* also provides a number of shell functions:
+
+.. code-block:: sh
+
+   # --- message ---
+   #
+   # void veinfo ( message )
+   #  Prints a message to stdout if $DEBUG is set to 'y'.
+   #
+   # void einfo  ( message )
+   #  Prints a message to stdout if $VERBOSE is set to 'y'.
+   #
+   # void ewarn  ( message )
+   #  Prints a message to stderr unless $QUIET is set to 'y'.
+   #
+   # void eerror ( message )
+   #  Prints a message to stderr.
+   #
+   #
+   # --- core ---
+   #
+   # @noreturn die ( [message], [exit_code] ), raises exit()
+   #  Lets the script die with the given message/exit code.
+   #
+   # @noreturn OUT_OF_BOUNDS(), raises die()
+   #  Lets the script die due to insufficient arg count.
+   #
+   # int run_command ( *cmdv )
+   #  Logs a command and runs it afterwards.
+   #
+   # int run_command_logged ( *cmdv )
+   #  Logs a command, runs it and logs the result.
+   #
+   # void autodie ( *cmdv ), raises die()
+   #  Runs a command. Lets the script die if the command fails.
+   #
+   #
+   # void load_functions ( *filenames, **SHLIB ), raises die()
+   #  Loads additional shell functions file(s) from $SHLIB.
+   #  (Referenced by $lf.)
+   #
+   # void dont_run_as_root(), raises die()
+   #  Lets the script die if it is run as root.
+   #
+   # int list_has ( word, *list_items )
+   #  Returns 0 if $word is in the given list, else 1.
+   #
+   # int qwhich ( *command )
+   #  Returns 0 if all listed commands are found by "which", else 1.
+   #
+   #
+   # --- fs ---
+   #
+   # int dodir ( *dir )
+   #  Ensures that zero or more directories exist by creating them if
+   #  necessary. Returns the number of directories that could not be created.
+   #
+   #
+   # --- str ---
+   #
+   # int yesno ( word, **YESNO_YES=0, **YESNO_NO=1, **YESNO_EMPTY=2 )
+   #  Returns $YESNO_YES if $word means "yes", $YESNO_EMPTY if $word is empty
+   #  and $YESNO_NO otherwise (if $word probably means "no").
+   #
+   # ~int str_trim ( *args )
+   #  Removes whitespace at the beginning and end of a string and replaces
+   #  any whitespace sequence within the string with a single space char.
+   #  Passes the return value of the underlying sed command.
+   #
+   # ~int str_upper ( *args )
+   #  Echoes the uppercase variant of stdin or *args.
+   #  Passes tr's return value.
+   #
+   # ~int str_lower ( *args )
+   #  Echoes the lowercase variant of stdin or *args.
+   #  Passes tr's return value.
+   #
+   # ~int str_field ( fieldspec, *args, **FIELD_SEPARATOR=' ' )
+   #  Echoes the requested fields of stdin or *args.
+   #  Passes cut's return value.
+   #
+   #
+   # --- int ---
+   #
+   # int is_int ( word )
+   #  Returns 0 if $word is an integer, else 1.
+   #
+   # int is_natural ( word )
+   #  Returns 0 if $word is an integer >= 0, else 1.
+   #
+   # int is_positive ( word )
+   #  Returns 0 if $word is an integer >= 1, else 1.
+   #
+   # int is_negative ( word )
+   #  Returns 0 if $word is an integer < 0, else 1.
+   #
+
+
+------------------------
+ Adding a function file
+------------------------
+
+Function files are shell script files that provide functions and variables.
+They should, however, not execute any code directly.
+
+The template below illustrates how to write function files:
+
+..  code-block:: sh
+
+   # protect against repeated inclusion of this file
+   # (replace <name> with a unique identifier)
+   if [ -z "${__HAVE_<name>__-}" ]; then
+   readonly __HAVE_<name>__=y
+
+   # function file body
+   # ...
+
+   fi
+
+Shell function files should be put into ``<ADDITIONS_DIR>/shlib``.
+
+---------------------
+ Adding a hook event
+---------------------
+
+Adding a new event has to be done in *roverlay's* source code and is a rather
+trivial task. The ``roverlay.hook`` module implements a function for running
+the event script:
+
+..  code-block:: python
+
+   # import hook module
+   import roverlay.hook
+
+   # ...
+   # then, somewhere in the code
+   roverlay.hook.run ( "<event>" )
+   # ...
+   roverlay.hook.run ( "<another event>" )
+
+
 =========================
  Configuration Reference
 =========================
@@ -1936,6 +2300,11 @@ DISTDIR_STRATEGY
 DISTDIR_VERIFY
    Alias to OVERLAY_DISTDIR_VERIFY_.
 
+.. _DISTMAP_COMPRESSION:
+
+DISTMAP_COMPRESSION
+   Alias to OVERLAY_DISTMAP_COMPRESSION_.
+
 .. _DISTMAP_FILE:
 
 DISTMAP_FILE
@@ -2051,6 +2420,13 @@ OVERLAY_DISTDIR_VERIFY
 
    Defaults to *no* as the verification is normally not needed.
 
+.. _OVERLAY_DISTMAP_COMPRESSION:
+
+OVERLAY_DISTMAP_COMPRESSION
+   Compression format for the distmap file. Choices are none, gzip/gz and
+   bzip2/bz2.
+
+   Defaults to bzip2.
 
 .. _OVERLAY_DISTMAP_FILE:
 
@@ -2212,9 +2588,10 @@ USE_EXPAND_RENAME
 .. _EVENT_HOOK:
 
 EVENT_HOOK
-   A script that is called for handling *events* (see Hooks_).
+   A script that is called for handling *events* (see `Event Hooks`_).
 
-   Defaults to ADDITIONS_DIR_/hooks/mux.sh.
+   Defaults to <libexec dir>/hooks/mux.sh if roverlay has been installed
+   and ADDITIONS_DIR_/hooks/mux.sh otherwise.
 
 .. _EVENT_HOOK_RESTRICT:
 
@@ -2226,6 +2603,10 @@ EVENT_HOOK_RESTRICT
 
    Defaults to <not set>, which is equivalent to *deny all*.
 
+   ``EVENT_HOOK_RESTRICT="overlay_success"`` would allow the ``overlay_success``
+   event only, whereas ``EVENT_HOOK_RESTRICT="* -overlay_success"`` would
+   allow any event except for ``overlay_success``. Also see `event policy`_.
+
 .. _FILTER_SHELL_ENV:
 
 FILTER_SHELL_ENV
@@ -3242,261 +3623,3 @@ Its mode of operation of operation is best described in pseudo-code:
 
 The dependency resolver can be **run as thread**, in which case the while loop
 becomes "loop until resolver closes".
-
-
-=======
- undef
-=======
-
-<<TODO; this section has to merged/moved>>
-
----------
- distmap
----------
-
-The distmap is a file that stores information about the files in the package
-mirror directory (`OVERLAY_DISTDIR_ROOT`_).
-<<TODO>>
-
-
--------
- hooks
--------
-
-*roverlay* calls a script when certain events occur, e.g. after successful
-overlay creation.
-
-<<TODO>>
-
-* real work is offloaded to the called script
-* roverlay provides some env vars
-* roverlay provides a *$FUNCTIONS* file and a way to load other function files
-* ``EVENT_HOOK_RESTRICT="this -not_that *"``
-
-<<^^TODO>>
-
-.. Note::
-
-   *roverlay* waits until the script terminates.
-
-
-++++++++++++++++++
- Hook environment
-++++++++++++++++++
-
-.. table:: environment variables provided by *roverlay*
-
-   +----------------+------------------+-----------------------------------------+
-   | variable       | source           | notes / description                     |
-   +================+==================+=========================================+
-   | PATH           | os.environ       |                                         |
-   +----------------+------------------+-----------------------------------------+
-   | LOGNAME        | os.environ       |                                         |
-   +----------------+------------------+-----------------------------------------+
-   | SHLVL          | os.environ       |                                         |
-   +----------------+------------------+-----------------------------------------+
-   | TERM           | os.environ       |                                         |
-   +----------------+------------------+-----------------------------------------+
-   | HOME           | os.environ       |                                         |
-   +----------------+------------------+-----------------------------------------+
-   | ROVERLAY_PHASE | event            | event that caused the script to run     |
-   +----------------+------------------+-----------------------------------------+
-   | OVERLAY        | config           | overlay directory (`OVERLAY_DIR`_),     |
-   +----------------+------------------+ initial working directory               |
-   | S              | *$OVERLAY*       |                                         |
-   +----------------+------------------+                                         |
-   | PWD            | *$OVERLAY*       |                                         |
-   +----------------+------------------+-----------------------------------------+
-   | DISTROOT       | config           | package mirror directory                |
-   |                |                  | (`OVERLAY_DISTDIR_ROOT`_)               |
-   +----------------+------------------+-----------------------------------------+
-   | TMPDIR         | os.environ,      | directory for temporary files           |
-   |                | *fallback*       |                                         |
-   +----------------+------------------+                                         |
-   | T              | *$TMPDIR*        |                                         |
-   +----------------+------------------+-----------------------------------------+
-   | ADDITIONS_DIR  | config           | directory with supplementary files      |
-   |                |                  | (`OVERLAY_ADDITIONS_DIR`_)              |
-   +----------------+------------------+                                         |
-   | FILESDIR       | *$ADDITIONS_DIR* |                                         |
-   +----------------+------------------+-----------------------------------------+
-   | SHLIB          | *$ADDITIONS_DIR* | directory with shell function files     |
-   |                |                  | (optional, only set if it exists)       |
-   +----------------+------------------+-----------------------------------------+
-   | FUNCTIONS      | *$ADDITIONS_DIR* | file with essential shell functions     |
-   |                |                  | (optional, only set if it exists)       |
-   +----------------+------------------+-----------------------------------------+
-   | DEBUG          | log level        | *shbool* (``y`` or ``n``) that          |
-   |                |                  | indicates whether debug messages should |
-   |                |                  | be printed                              |
-   +----------------+------------------+-----------------------------------------+
-   | VERBOSE        | log level        | *shbool*                                |
-   +----------------+------------------+-----------------------------------------+
-   | QUIET          | log level        | *shbool* that indicates whether scripts |
-   |                |                  | should be quiet                         |
-   +----------------+------------------+-----------------------------------------+
-   | NO_COLOR       | *n/a*            | *shbool*. Always set to *y* since       |
-   |                |                  | colored output should not be produced   |
-   +----------------+------------------+-----------------------------------------+
-   | NOSYNC         | config           | *shbool* that indicates whether data    |
-   |                |                  | transfers from/to remote machines is    |
-   |                |                  | allowed (NOSYNC_)                       |
-   +----------------+------------------+-----------------------------------------+
-   | EBUILD         | config           | the *ebuild* executable                 |
-   +----------------+------------------+-----------------------------------------+
-   | GIT_EDITOR     | *n/a*            | set to */bin/false*                     |
-   +----------------+------------------+                                         |
-   | GIT_ASKPASS    | *n/a*            |                                         |
-   +----------------+------------------+-----------------------------------------+
-
-
-The default *essential shell functions* file (*$FUNCTIONS*) makes,
-when included in the hook script, most of the enviroment variables readonly.
-
-
-.. table:: variables provided by *$FUNCTIONS*
-
-   +-----------------+-------------------------------------------------------+
-   | variable        | description                                           |
-   +=================+=======================================================+
-   | IFS_DEFAULT     | default *internal field separator*                    |
-   +-----------------+-------------------------------------------------------+
-   | IFS_NEWLINE     | *IFS* for iterating over text lines                   |
-   +-----------------+-------------------------------------------------------+
-   | DEVNULL         | */dev/null* target (could also be a file)             |
-   +-----------------+-------------------------------------------------------+
-   | EX_ERR          | default error exit code                               |
-   +-----------------+-------------------------------------------------------+
-   | EX_ARG_ERR      | default exit code for arg errors                      |
-   +-----------------+-------------------------------------------------------+
-   | SCRIPT_FILENAME | file name of the hook script                          |
-   +-----------------+-------------------------------------------------------+
-   | SCRIPT_NAME     | name of the hook script (without file extension)      |
-   +-----------------+-------------------------------------------------------+
-   | lf              | reference to a function that loads additional shell   |
-   |                 | function files                                        |
-   +-----------------+-------------------------------------------------------+
-
-
-*$FUNCTIONS* also provides a number of shell functions:
-
-.. code-block:: sh
-
-   # --- message ---
-   #
-   # void veinfo ( message )
-   #  Prints a message to stdout if $DEBUG is set to 'y'.
-   #
-   # void einfo  ( message )
-   #  Prints a message to stdout if $VERBOSE is set to 'y'.
-   #
-   # void ewarn  ( message )
-   #  Prints a message to stderr unless $QUIET is set to 'y'.
-   #
-   # void eerror ( message )
-   #  Prints a message to stderr.
-   #
-   #
-   # --- core ---
-   #
-   # @noreturn die ( [message], [exit_code] ), raises exit()
-   #  Lets the script die with the given message/exit code.
-   #
-   # @noreturn OUT_OF_BOUNDS(), raises die()
-   #  Lets the script die due to insufficient arg count.
-   #
-   # int run_command ( *cmdv )
-   #  Logs a command and runs it afterwards.
-   #
-   # int run_command_logged ( *cmdv )
-   #  Logs a command, runs it and logs the result.
-   #
-   # void autodie ( *cmdv ), raises die()
-   #  Runs a command. Lets the script die if the command fails.
-   #
-   #
-   # void load_functions ( *filenames, **SHLIB ), raises die()
-   #  Loads additional shell functions file(s) from $SHLIB.
-   #  (Referenced by $lf.)
-   #
-   # void dont_run_as_root(), raises die()
-   #  Lets the script die if it is run as root.
-   #
-   # int list_has ( word, *list_items )
-   #  Returns 0 if $word is in the given list.
-   #
-   # int qwhich ( *command )
-   #  Returns 0 if all listed commands are found by "which".
-   #
-   #
-   # --- fs ---
-   #
-   # int dodir ( *dir )
-   #  Ensures that zero or more directories exist by creating them if
-   #  necessary. Returns the number of directories that could not be created.
-   #
-   #
-   # --- str ---
-   #
-   # int yesno ( word, **YESNO_YES=0, **YESNO_NO=1, **YESNO_EMPTY=2 )
-   #  Returns $YESNO_YES if $word means "yes", $YESNO_EMPTY if $word is empty
-   #  and $YESNO_NO otherwise (if $word probably means "no").
-   #
-   # ~int str_trim ( *args )
-   #  Removes whitespace at the beginning and end of a string and replaces
-   #  any whitespace sequence within the string with a single space char.
-   #  Passes the return value of the underlying sed command.
-   #
-   # ~int str_upper ( *args )
-   #  Echoes the uppercase variant of stdin or *args.
-   #  Passes tr's return value.
-   #
-   # ~int str_lower ( *args )
-   #  Echoes the lowercase variant of stdin or *args.
-   #  Passes tr's return value.
-   #
-   # ~int str_field ( fieldspec, *args, **FIELD_SEPARATOR=' ' )
-   #  Echoes the requested fields of stdin or *args.
-   #  Passes cut's return value.
-   #
-   #
-   # --- int ---
-   #
-   # int is_int ( word )
-   #  Returns 0 if $word is an integer, else 1.
-   #
-   # int is_natural ( word )
-   #  Returns 0 if $word is an integer >= 0, else 1.
-   #
-   # int is_positive ( word )
-   #  Returns 0 if $word is an integer >= 1, else 1.
-   #
-   # int is_negative ( word )
-   #  Returns 0 if $word is an integer < 0, else 1.
-   #
-
-
-+++++++++++++++++++++
- Adding a hook event
-+++++++++++++++++++++
-
-in roverlay
-
-..  code-block:: python
-
-   # import hook module
-   import roverlay.hook
-
-   # ...
-   # then:
-   roverlay.hook.run ( "<event>" )
-   # ...
-   roverlay.hook.run ( "<another event>" )
-
-
-in additions dir (assuming that mux.sh is used)
-
-..  code-block:: text
-
-   <somehow create> ${ADDITIONS_DIR}/<hook>.<event>
-   <somehow create> ${ADDITIONS_DIR}/<hook>/<event>.sh