Obtain a temporary buffer for use by the ObjectInserter or its subclass.
This buffer is supplied by the ObjectInserter base class to itself and
its subclasses for the purposes of pulling data from a supplied
InputStream, passing it through a Deflater, or formatting the canonical
format of a small object like a small tree or commit.
This buffer IS NOT for translation such as auto-CRLF or content
filtering and must not be used for such purposes.
The returned buffer is small, around a few KiBs, and the size may change
between versions of JGit. Callers using this buffer must always check the
length of the returned array to ascertain how much space was provided.
There is a single buffer for each ObjectInserter, repeated calls to this
method will (usually) always return the same buffer. If the caller needs
more than one buffer, or needs a buffer of a larger size, it must manage
that buffer on its own.
The buffer is usually on first demand for a buffer.