Before attempting to mount a GIO-backed volume, check if it is not
already mounted. Once the file has been retrieved, unmount the
volume only if we mounted it, but leave it mounted if it already was.
Allow to override the OUTFILE parameter in the configuration file
with a -o, --output option on the command line. Also detect if no
output file has been specified, either in the configuration file
or on the command line.
Allow to specify a base filename (without extension) to the -c
option. A .conf extension will automatically be added when looking
for a configuration file in the XDG directory.
Spawn a shell (or any command specified on the command line) once
the secret has been reconstituted and wait for the child process
to terminate, then delete the secret.
Damien Goutte-Gattat