Check specific data file, not the parent folder

[brfi3983]

https://github.com/jouvetg/igm/blob/bf635958b8e9c5aff019b7ada2a215d48a0cc3b4/igm/common.py#L436C1-L436C40

In the current implementation, even if you have different names for each of your input.nc files, it will not download the new data as it only checks the parent folder data. Instead, download the data but save it to a more specific filename such as aletsch_basic.nc and then check if that specific file exists, not the folder.

This can be done by changing the name of the input.nc file to the specific name in the cloud and then reading that name within the python script before doing the checks.

Lastly, change the print() in the else code block to a raise() call for a more robust error handling and correct the following typo: The data already existing at {folder_name} -> The data already exists at {}.