resolves #988 consistently format origin information in log and error messages

• include reftype on source in structured log message
• use reftype as field name for refname in pretty log message and error message
• qualify remote tracking branches taken from local repository in pretty log message
• use local as field name for gitdir of local repository in structured log message
• use gitdir as location of local repository in pretty log message
• remove tag/ prefix from refname in error message thrown by content aggregator
• indent detail in error message for duplicate file by 4 spaces