bcftools merge: support single-file edge case [enhancement] #2100
Description
If bcftools merge is called with only a single vcf file, it fails with:
About: Merge multiple VCF/BCF files from non-overlapping sample sets to create one multi-sample file
Note that only records from different files can be merged, never from the same file. For "vertical" merge
take a look at "bcftools norm" instead.
Usage: bcftools merge [options] <A.vcf.gz> <B.vcf.gz> [...]
This is quite a useful error message.
However, since I have to merge a varying number of vcf files for a large number of sets of vcf files with various cardinality, including 1 but thankfully not 0, I currently need check the number of files for each set upfront and use cp /bcftools view instead if the current set has only one file. Therefore, I thik it would be great if bcftools merge would only warn, not error in the single file case, i.e if usage was relaxed to Usage: bcftools merge [options] <A.vcf.gz> [<B.vcf.gz>] [...]