Issue with location of `backup-tmp`

[lemzwerg]

[63e33df]
[openSUSE Leap 15.6]

While the backup.sh script lets me select a location for the compressed backup, it uses the current directory for the backup-tmp tree. This is non-standard. Normally, such a directory tree should be placed into the directory specified by the TMPDIR enironment variable. It should also have a unique postfix to not interfere with parallel runs (for whatever reason).

Two solutions come immediately to my mind: the script might automatically use TMPDIR, or it might offer a dialogue to select a location for this directory. An additional bonus would be to check whether there is enough space for holding the uncompressed data from the phone.