Fail if output type does not match file extension

[Will-Tyler]

Description

In #66, @tomwhite suggests that vcztools should fail if the user tries to write the output (which is uncompressed VCF) to a file path with an extension that does not correspond to uncompressed VCF (e.g. .bcf or .vcz.gz).

In bcftools, the user can specify both the ouput file (with -o) and the output format (with -O). If the user specifies an output type that is different from the output type indicated by the output file's extension, then bcftools uses the output type indicated by the extension.

Since vcztools only supports uncompressed VCF at the moment, vcztools should fail if the output type indicated by the output file's extension is not uncompressed VCF.

References

• bcftools common options