more gas change thoughts

[Dirk Hohndel]

Here's a very simple scenario that I think shows that internally we should
manage gaschanges by gasidx and not by gas.

Consider this example:

you dive with air and EAN80 set up on your computer. Later you realize
that you had EAN75 in your tank. Oops. I hope you're not bent.

So now the dive is downloaded with the gas change and you edit the
equipment to list the correct gas. But your gas change is still to (a now
nonexistant) EAN80.

Thoughts?

/D