revert(3p/git): Revert merge of git upstream at v2.26.2

This causes cgit to serve error pages, which is undesirable.

This reverts commit 5229c9b232, reversing
changes made to f2b211131f.

third_party/git/t/t0090-cache-tree.sh

@@ -21,10 +21,9 @@ generate_expected_cache_tree_rec () {
 	parent="$2" &&
 	# ls-files might have foo/bar, foo/bar/baz, and foo/bar/quux
 	# We want to count only foo because it's the only direct child
-	git ls-files >files &&
-	subtrees=$(grep / files|cut -d / -f 1|uniq) &&
+	subtrees=$(git ls-files|grep /|cut -d / -f 1|uniq) &&
 	subtree_count=$(echo "$subtrees"|awk -v c=0 '$1 != "" {++c} END {print c}') &&
-	entries=$(wc -l <files) &&
+	entries=$(git ls-files|wc -l) &&
 	printf "SHA $dir (%d entries, %d subtrees)\n" "$entries" "$subtree_count" &&
 	for subtree in $subtrees
 	do