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 <[email protected]>
Signed-off-by: Elijah Newren <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: newren

builtin/sparse-checkout.c

@@ -112,7 +112,9 @@ static int update_working_directory(struct pattern_list *pl)
 
 	repo_hold_locked_index(r, &lock_file, LOCK_DIE_ON_ERROR);
 
+	setup_unpack_trees_porcelain(&o, "sparse-checkout");
 	result = update_sparsity(&o);
+	clear_unpack_trees_porcelain(&o);
 
 	if (result == UPDATE_SPARSITY_WARNINGS)
 		/*

t/t1091-sparse-checkout-builtin.sh

@@ -328,12 +328,10 @@ test_expect_success 'sparse-checkout (init|set|disable) warns with dirty status'
 	echo dirty >dirty/folder1/a &&
 
 	git -C dirty sparse-checkout init 2>err &&
-	test_i18ngrep "error" err &&
-	test_i18ngrep "Cannot update sparse checkout" err &&
+	test_i18ngrep "error.*Cannot update sparse checkout" err &&
 
 	git -C dirty sparse-checkout set /folder2/* /deep/deeper1/* 2>err &&
-	test_i18ngrep "error" err &&
-	test_i18ngrep "Cannot update sparse checkout" err &&
+	test_i18ngrep "error.*Cannot update sparse checkout" err &&
 	test_path_is_file dirty/folder1/a &&
 
 	git -C dirty sparse-checkout disable 2>err &&