Draft: Cat file use batch command

Starting in git 2.36, git-cat-file gained an option --batch-command.

Previously, in order to get the object metadata versus the object contents, two separate options had to be used in --batch and --batch-check. This meant that we had to keep two git processes around per repository--one to get the metadata, and one to potentially get the contents. Now with --batch-command, we can consolidate to just using one git-cat-file process instead of two.

NOTE: the commits in this MR should be squashed into a single commit when merged. But, splitting them up makes it a little easier to review.