Sometimes when we use `git cat-file --batch-all-objects`, we only want data of type "blob". In order to filter them out, we may need to use some additional processes (such as `git rev-list --objects --filter=blob:none --filter-provided-objects`) to obtain the SHA of all blobs, and then use `git cat-file --batch` to retrieve them. This is not very elegant, or in other words, it might be better to have an internal implementation of filtering within `git cat-file --batch-all-objects`. However, `git cat-file` already has a `--filters` option, which is used to "show content as transformed by filters". I'm not sure if there is a better word to implement the functionality of filtering by type? For example, `--type-filter`? Thanks, -- ZheNing Hu
