docs/gitcredentials: describe URL prefix matching
Documentation was inaccurate since 9a121b0d226 (credential: handle
`credential.<partial-URL>.<key>` again, 2020-04-24)
Add tests for documented behaviour.
Signed-off-by: M Hickford <mirth.hickford@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
authored by