fetch: add --negotiation-restrict option

fetch: add --negotiation-restrict option

The --negotiation-tip option to 'git fetch' and 'git pull' allows users
to specify that they want to focus negotiation on a small set of
references. This is a _restriction_ on the negotiation set, helping to
focus the negotiation when the ref count is high. However, it doesn't
allow for the ability to opportunistically select references beyond that
list.

This subtle detail that this is a 'maximum set' and not a 'minimum set'
is not immediately clear from the option name. This makes it more
complicated to add a new option that provides the complementary behavior
of a minimum set.

For now, create a new synonym option, --negotiation-restrict, that
behaves identically to --negotiation-tip. Update the documentation to
make it clear that this new name is the preferred option, but we keep
the old name for compatibility. Mark --negotiation-tip as an alias of the
new, preferred option.

Update a few warning messages with the new option, but also make them
translatable with the option name inserted by formatting. At least one
of these messages will be reused later for a new option.

Reviewed-by: Matthew John Cheetham <mjcheetham@outlook.com>
Signed-off-by: Derrick Stolee <stolee@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>