I would like to extract VCF subset with only those variants that are present in one particular sample. E.g. i have three sample VCF with ten variants. Only one variant has been detected in the first sample, so i would like to subset VCF so that only this variant is kept.
Pseudo code would be something like:

    bcftools query -f'%CHROM:%POS %INFO [%GT]\n' -i'GT="alt in sample1"' file.vcf

The desired output is VCF with three samples but only variants present in one of the samples, in this case `sample1`


Alternative solution is to use `bcftools +split` plugin, e.g.:

    bcftools +split file.vcf -Ob -o testDir -i'GT="alt"'


