bug#74994: Improve Emacs iCalendar support

[Richard Lawrence <rwl@recursewithless.net>]

Jean Louis <bugs@gnu.support> writes:

> I am using development Emacs version, is patch for it?

Yes, it was generated against Emacs master (commit 07cc8abca75 at the
time I generated the patches).

> I don't know how to apply your patch. Can you tell me step by step?

To be honest I'm new to the patch workflow myself but it should be:

  git apply path/to/the/patch

run from the repository root, on the master branch. If you want to try
out icalendar-mode, do this for both patches in succession (the second
patch, which provides icalendar-mode, requires the code introduced in
the first).

To run the test suite and verify that it works: make check

(Please let me know here if you see any errors in
test/lisp/calendar/icalendar-parser-tests.log)

There aren't many user-facing functions yet, but if you want to test the
code with some iCalendar data you have in file, do M-x find-file
path/to/file; activate icalendar-mode if it doesn't activate
automatically; say "y" to unfold lines if asked (Note: there is
currently a bug where you may get asked multiple times; if you've
already got the data in an unfolded buffer and get asked again, you can
say "n"; I still need to look into this); and then, in the unfolded
buffer, try calling functions like this (e.g. with M-:): 

(icalendar-parse-component (point-max)), with point at the start of a
"BEGIN:..." line, e.g. at the start of BEGIN:VCALENDAR if you want to
parse a whole calendar.

(icalendar-parse-property (line-end-position)), with point at the start
of a property line 

If you get any parse errors, please let me know here!

Best,
Richard