Revoking a share meant opening the share dialog, removing each person
from it in turn, and saving. That is the right tool for changing who has
access and the wrong one for withdrawing it altogether, which is the more
urgent of the two and the one someone is likely to want in a hurry.
Both now offer "Stop sharing" in the context menu, which clears the lot
after a confirmation saying how many people lose access. It appears only
when there is something to revoke, so the menu says whether a thing is
shared as well as offering to change it.
A calendar also says it is shared now. Address books have carried that
badge since they gained sharing; calendars never did, so the only way to
find out was to open the dialog and look -- which for the owner of a
dozen calendars means opening a dozen dialogs.
Both go through the existing update paths, so a server that refuses is
reported rather than swallowed.
Verified against the mock, both kinds: sharing one shows the badge and
adds the entry, confirming clears `shareWith`, the badge goes, and the
entry disappears with it since there is no longer anything to stop.