I'm about to run samtools sort (version 1.6) and I'm reviewing the available configuration options.
$ samtools sort Usage: samtools sort [options...] [in.bam] Options: -l INT Set compression level, from 0 (uncompressed) to 9 (best) -m INT Set maximum memory per thread; suffix K/M/G recognized [768M] -n Sort by read name -t TAG Sort by value of TAG. Uses position as secondary index (or read name if -n is set) -o FILE Write final output to FILE rather than standard output -T PREFIX Write temporary files to PREFIX.nnnn.bam --input-fmt-option OPT[=VAL] Specify a single input file format option in the form of OPTION or OPTION=VALUE -O, --output-fmt FORMAT[,OPT[=VAL]]... Specify output format (SAM, BAM, CRAM) --output-fmt-option OPT[=VAL] Specify a single output file format option in the form of OPTION or OPTION=VALUE --reference FILE Reference sequence FASTA FILE [null] -@, --threads INT Number of additional threads to use 
I'm curious about the
--reference flag. I've never used it before with
samtools sort and I'm wondering what behavior it invokes. The online documentation doesn't even mention the flag. Under what circumstances would I want/need to specify the reference genome?