Write a file’s content into the object store and get its SHA back, without committing anything. Needed for binary content, which a tree entry cannot carry inline; for text, putting content straight on the tree entry is one call fewer. Up to 100 MB.
The encoding used for content. Currently, utf-8 and base64 are supported. GitHub uses utf-8 when this is absent — pass base64 with base64-encoded content for a binary file.