Create a stream to write a new blob into the object db

This function may need to buffer the data on disk and will in general not be the right choice if you know the size of the data to write. If you have data in memory, use git_blob_create_frombuffer(). If you do not, but know the size of the contents (and don't want/need to perform filtering), use git_odb_open_wstream().

Don't close this stream yourself but pass it to git_blob_create_fromstream_commit() to commit the write to the object db and get the object id.

If the hintpath parameter is filled, it will be used to determine what git filters should be applied to the object before it is written to the object database.