Update docs on write_timeseries_dsg to ignore overwrite if add_to_existing is TRUE

[doi-usgs]

Update docs on write_timeseries_dsg to ignore overwrite if add_to_existing is TRUE

[dblodgett-usgs]

I remember this being a really annoying detail and just made it force the user to be really explicit.

Am rereading the documentation and don't really see where you think I would change it... :/

[jordansread]

From the docs it is unclear what happens when you have add_to_existing = TRUE and overwrite = TRUE. Based on you telling me people need to be really explicit, I am assuming the existing file is deleted and the add_to_existing arg is ignored.

I haven't played around with this though. I guess it errors if the file exists and overwrite is TRUE? Why wouldn't it just overwrite it if that is the case? From docs:

overwrite       boolean error if file exists

[dblodgett-usgs]

So this is all the logic for overwrite and add to existing.

  if(!overwrite & !add_to_existing & file.exists(nc_file)) stop("File already exists and overwrite is false.")
  if(overwrite & !add_to_existing) unlink(file.exists(nc_file))
  if(add_to_existing & !file.exists(nc_file)) add_to_existing=FALSE

• if you set overwrite = TRUE and add_to_existing = TRUE it won't delete the file and will add to it.
• If you set overwrite = FALSE and add_to_existing = TRUE it won't touch the file and will add to it.
• If you set overwrite = TRUE and add_to_existing = FALSE it will delete the file and start fresh.
• If you set overwrite = FALSE and add_to_existing = FALSE and the file exists, it will error, otherwise it will create a fresh file.

These seem logical to me and the docs make OK sense.

I modified the docs for overwrite to read: overwrite: boolean unless set to true, error if file exists.

With that change, do you think we can close this issue?