Argument handling improvement

[jonblau]

I first thought I'd post an issue, but since it was pretty simple, I solved it myself.

Despite a long list of conditions, not all cases were previously handled correctly. For example, if the command was just edcre -s 15 without the track bin file, it was interpreting 15 as the track name and complained it couldn't be found.

The "rules" are these:

• the track should be the last argument
• -v, -t, or -k should not be the last argument
• -s should be followed by a minimum of two arguments, not just one
• there may be up to seven arguments, not just six

So I tried to make to code more efficient and removed some code duplication. Error messages like the one for -s may also be added later for -v, -t, -k.

One downside though: you can not use tracks that are also named -v, -t, or -k...

[alex-free]

If we want to be really fancy, we can still allow for tracks named '-v', '-t', or '-k' it's not impossible. The way to do it would be to first seeing if fopen is successful in opening a file named as such, and on failure (silently, no need to tell the user we are trying to open a file named '-v') to then treat it as an improper usage of the argument.

Thanks for the contribution, I definitely forgot that 7 args is now possible with -k being included.

[jonblau]

Ok, I have created a small function with your idea, which now allows to use files that are also named -v -t -k or -s and identify syntax errors at the same time. I think we're good.