Read a file from the working folder of a repository
and write it to the Object Database as a loose blob
@param id return the id of the written blob
@param repo repository where the blob will be written.
this repository cannot be bare
@param relative_path file from which the blob will be created,
relative to the repository's working dir
@return 0 or an error code
Read a file from the working folder of a repository and write it to the Object Database as a loose blob
@param id return the id of the written blob @param repo repository where the blob will be written. this repository cannot be bare @param relative_path file from which the blob will be created, relative to the repository's working dir @return 0 or an error code