Add warning upon entry of identical data

[saemiw]

We had sometimes to problem that field workers forgot/confused that they already imported data from a certain tablet. They then copied and synchronised the same data again and finally ended up with 2 rows of the same data set. It would be nice to have some warnings like "an identical data entry already exists, are you sure you want to synronise?" or some the like. This idea probably need some more thought but some kind of checks to prevent double synchronisation would be a nice improvement one day.

[m-kuhn]

This is pretty close to one of the design limitations of the offline editing code. But I guess still on the side that can be solved.

[saemiw]

O.k. good to know.

As a reminder: If QFieldSync was to synchronise directly on the device (instead of packing files that need copy'n'pasting) this could probably reduce the risk of double synchronisation. See discussion here https://github.com/opengisch/QField/issues/370

[m-kuhn]

On the contrary, if QField would sync directly, it could keep track of what is synced already and make sure it's not synced again. Whereas now, someone can easily sync the same files twice.

[saemiw]

More precision on this issue: A possible solution (discussed with @m-kuhn) could involve the use of MD5 hashes that allows checking if an identical file has already been synchronised. If this is the case a warning message should be triggered. (side remark: I am thinking in synrhonising geopackage files set offline).

The information what files were alsready synchronised should be stored in the "mother project" (i.e. the project from where the data were set offline and are now synchronised back to).

[OBVYamaska]

Old issue, but any improvement?
We are looking for a solution on a similar issue (#577).

Also, some users will sync their project from QField, but use the same project back on their tablet and take new data in the field. Of course, when they try to sync back this project, the first datas that were synced once are still recognized as "new" data by the plugin, creating duplicates. I'm wondering it the plugin could repackage these datas to the QField project as part of the original package (restart the log) after a sync, so the same project could be used again and again without the need to repackage everytime? This is a clear limitation for the level of our users right now.