Feature suggestion: Check for existence and format of all required files at startup in addition to first use.

[Alan Hoyle]

I'm trying to index a genome but this probably applies to other modes as well.

In my STAR --runMode genomeGenerate [...] command line, I've had a couple of minor typos that cause the process to fail.

Specifically, I had a typo in specifying the path to the GTF file. The issue I've run into is that STAR happily runs along, creating the Suffix Array and running for hours, but then it runs into the missing GTF file, and just does a fatal error.

It would be much more user friendly if STAR checked for the existence of required files at run initiation, so that it would die immediately as opposed to waiting for significant processing to happen before dying. I'd rather shoot myself in the foot quickly rather than having to wait a couple hours.

I had to run it a third time as I had neglected to gunzip the .gtf.gz.