First-ever-transition hint about auto-save (and/or a Save As option on first edit)

[pedropintosilva]

Initially reported by @mmeeks

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When you click "Edit", auto-save turns on. From that moment, any change (even a typo from your cat walking on the keyboard) gets written back to the file immediately. You can't close-without-saving to escape it.

How to improve it so, we are more in line with what user expects: The very first time a user ever switches from view to edit, pop up a small one-time message that says something like:

"You're now editing. Your changes will save automatically. Want to save a copy first?" [Save As…] [Got it]

or much shorter "Auto-save is on. Save a copy first?" [Save As…] [Dismiss] "

We actually already have a snackbar so it should be very easy to do this.

[mmeeks]

Sounds nice to use the snack-bar; we could also ensure that auto-save is actually suspended from the change until they responded to / dismissed that / we hid it after a time (?)

I also expect that some files are edited quite frequently and there is no point in annoying the user; whereas some files are 'old' and are unlikely to want to be touched; I strongly expect the editing modality of documents to be that files are touched, and then discarded and not touched again for years if ever.

I wonder if we should snack-bar only on files that have not been edited for a week or so; sadly we don't have good data to inform the roll-over point there but ... ;-) "This file has not been changed , would you like to edit a copy ?" - so it is more of a "you missed an attachment to your E-mail" type warning :-)