RelNotes/2.2.0.txt: fix minor typos

Signed-off-by: Matthieu Moy <Matthieu.Moy@imag.fr>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Documentation: typofixes

In addition to fixing trivial and obvious typos, be careful about
the following points:

 - Spell ASCII, URL and CRC in ALL CAPS;
 - Spell Linux as Capitalized;
 - Do not omit periods in "i.e." and "e.g.".

Signed-off-by: Thomas Ackermann <th.acker@arcor.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
t3312-notes-empty: Test that 'git notes' removes empty notes by default

Add test cases documenting the current behavior when trying to
add/append/edit empty notes. This is in preparation for adding
--allow-empty; to allow empty notes to be stored.

Signed-off-by: Johan Herland <johan@herland.net>
notes: Add --allow-empty, to allow storing empty notes

Although the "git notes" man page advertises that we support binary-safe
notes addition (using the -C option), we currently do not support adding
the empty note (i.e. using the empty blob to annotate an object). Instead,
an empty note is always treated as an intent to remove the note
altogether.

Introduce the --allow-empty option to the add/append/edit subcommands,
to explicitly allow an empty note to be stored into the notes tree.

Also update the documentation, and add test cases for the new option.

Reported-by: James H. Fisher <jhf@trifork.com>
Improved-by: Kyle J. McKay <mackyle@gmail.com>
Signed-off-by: Johan Herland <johan@herland.net>