sparse-checkout: use improved unpack_trees porcelain messages
setup_unpack_trees_porcelain() provides much improved error/warning
messages; instead of a message that assumes that there is only one path
with a given problem despite being used by code that intentionally is
grouping and showing errors together, it uses a message designed to be
used with groups of paths. For example, this transforms
error: Entry ' folder1/a
folder2/a
' not uptodate. Cannot update sparse checkout.
into
error: Cannot update sparse checkout: the following entries are not up to date:
folder1/a
folder2/a
In the past the suboptimal messages were never actually triggered
because we would error out if the working directory wasn't clean before
we even called unpack_trees(). The previous commit changed that,
though, so let's use the better error messages.
Reviewed-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>