* calendar/todos.el Add and revise further doc strings and

* calendar/todos.el Add and revise further doc strings and
comments; major code rearrangement.
(todos-merged-files, todos-prompt-merged-files)
(todos-print-priorities, todos-tmp-buffer-name)
(todos-top-priorities-widgets, todos-update-merged-files)
(todos-merged-top-priorities, todos-merged-diary-items)
(todos-merged-regexp-items, todos-merged-custom-items)
(todos-raw-mode, todos-change-default-file)
(todos-toggle-diary-inclusion, todos-toggle-item-diary-nonmarking)
(todos-toggle-diary-nonmarking, todos-validate-category-name):
Remove.
(todos-category-string-matcher): Comment out.
(todos-categories): New defgroup.
(todos-initial-file, todos-filter-buffer)
(todos-top-priorities-buffer, todos-categories-category-label)
(todos-diary-items-buffer, todos-regexp-items-buffer)
(todos-custom-items-buffer, todos-filter-files)
(todos-highlight-item, todos-todo-mode-date-time-regexp):
New defcustoms.
(todos-diary-expired): New face.
(todos-print-buffer, todos-multiple-files)
(todos-multiple-files-widget, todos-key-bindings): New variables.
(todos-short-file-name, todos-reevaluate-default-file-defcustom)
(todos-special-buffer-name)
(todos-reevaluate-filter-files-defcustom)
(todos-reset-highlight-item, todos-reevaluate-defcustoms)
(todos-nondiary-marker-matcher, todos-diary-nonmarking-matcher)
(todos-diary-expired-matcher, todos-category-string-matcher-1)
(todos-category-string-matcher-2, todos-repair-categories-sexp)
(todos-validate-name, todos-multiple-files)
(todos-display-categories-1, todos-update-categories-display)
(todos-modes-set-3, todos-mode-external-set): New functions.
(todos-set-top-priorities-in-file)
(todos-set-top-priorities-in-category)
(todos-top-priorities-multifile, todos-diary-items-multifile)
(todos-regexp-items-multifile, todos-custom-items-multifile)
(todos-convert-legacy-files, todos-jump-to-item)
(todos-edit-multiline-item, todos-edit-item-date-from-calendar)
(todos-edit-item-diary-inclusion)
(todos-edit-category-diary-inclusion)
(todos-edit-item-diary-nonmarking)
(todos-edit-category-diary-nonmarking): New commands.
(todos, todos-faces): Update :version.
(todos-done-separator, todos-completion-ignore-case):
Change default value.
(todos-done-separator): Change :set function.
(todos-indent-to-here): Add :validate function to :type.
(todos-prefix-string, todos-mark, todos-button)
(todos-sorted-column, todos-archived-only, todos-search)
(todos-done, todos-done-sep): Provide full face definitions
instead of inheriting.
(todos-edit-buffer, todos-categories-buffer): Change from
defcustom to defvar.
(todos-category-beg, todos-category-done): Change from defvar to
defconst.
(todos-files): Check if todos-files-directory exists.
(todos-default-todos-file, todos-mode-line-control, todos-print):
Use todos-short-file-name.
(todos-font-lock-keywords): Use todos-nondiary-marker-matcher,
todos-diary-nonmarking-matcher, todos-category-string-matcher-1,
todos-category-string-matcher-2, todos-diary-expired-matcher.
(todos-category-select): Use todos-done-string-start, and
condition search on todos-show-with-done; don't make display
overlay for done items separator string if there already is one;
use todos-highlight-item, require hl-line and activate
hl-line-mode here in order to avoid a hang if done in todos-mode
or the mode hook.
(todos-update-categories-sexp): Use todos-categories-full if set,
otherwise todos-categories.
(todos-make-categories-list): Don't test for archive file when
processing a legacy todo-mode file.
(todos-check-format): Add check for todos-categories sexp.
(todos-diary-item-p): Use todos-nondiary-start instead of
todos-date-pattern.
(todos-marked-item-p): Rename from todos-item-marked-p.
(todos-read-file-name): Don't accept empty name; validate.
(todos-read-category): Validate new name before prompting whether
to add new category; force quit if user answers no.
(todos-filter-items): Improve implementation.
(todos-set-top-priorities): Rewrite as a noninteractive function
using minibuffer input instead of widgets.
(todos-insert-sort-button): Call todos-display-sorted with
argument nil to display categories in numerical order, instead of
calling todos-display-categories.
(powerset-recursive): Borrow and slightly reformulate the (GDFL'd)
Common Lisp powerset function at
http://rosettacode.org/wiki/Power_set#Common_Lisp.
(powerset-bitwise): Implement in Emacs Lisp the (GDFL'd) C
powerset function at http://rosettacode.org/wiki/Power_set#C.
(todos-powerset): Defalias to powerset-bitwise.
(todos-mode-map): Generate from todos-key-bindings instead of
listing each key definition.
(todos-categories-mode-map): Add two bindings.
(todos-filter-items-mode-map): Add some bindings, remove others.
(todos-mode): Derive from special-mode; use todos-modes-set-3; add
function setting todos-done-separator to
window-configuration-change-hook.
(todos-unload-hook): Remove function setting todos-done-separator
from window-configuration-change-hook.
(todos-archive-mode): Derive from todos-mode; use todos-modes-set-3.
(todos-edit-mode): Derive from text-mode; use todos-mode-external-set.
(todos-categories-mode): Derive from special-mode; use
todos-mode-external-set.
(todos-filter-items-mode): Derive from special-mode.
(todos-quit): Save archive file if it hasn't yet been saved.
(todos-display-categories): Delegate all functionality to
todos-display-categories-1 and todos-update-categories-display.
(todos-toggle-view-done-items): Improve implementation.
(todos-highlight-item): Require hl-line.
(todos-toggle-display-date-time): Remove argument and make it
apply only to whole file.
(todos-top-priorities, todos-diary-items, todos-regexp-items)
(todos-custom-items): Use todos-special-buffer-name.
(todos-add-file): Use todos-short-file-name and
todos-reevaluate-defcustoms; remove validation, since it's now
done in todos-read-file-name.
(todos-add-category): Also update todos-categories-full if non-nil.
(todos-delete-category): Delete file after confirmation if only
category is deleted.
(todos-move-category): Use todos-short-file-name and
todos-reevaluate-defcustoms.
(todos-insert-item): Fix getting date from the calendar and
insertion of time string.
(todos-set-date-from-calendar): Enter calendar buffer, suppressing
display of diary entries.
(todos-edit-multiline): Add optional argument to restrict editing
buffer to current item, otherwise make entire buffer (i.e. whole
file) editable.
(todos-edit-quit): When whole file is editable, check file format
validity before killing buffer, and if valid, recalculate
categories sexp to be safe.
(todos-edit-item-header): Allow choosing date from calendar.
(todos-item-done): Handle marked items.