I tried to update roundcube today stopped with error. Log found here:
Sounds related to :
WARNING - The HOME or COMPOSER_HOME environment variable must be set for composer to run correctly
I recall that I saw this at least once in another app I believe … Maybe people from the apps group now more about this 
No big changes on that line since the previous version.
Don’t know why suddenly COMPOSER_HOME would be unset.
Manage arguments with getopts
ynh_handle_getopts_args “$@”
workdir="${workdir:-$final_path}"
Is the “-” before final path right?
Just a wild guess…
Discourse hide the real link… The link to the line I was showing is that !
To answer your specific question @mr_smithers, :- means if workdir is empty, use final_path instead.
Thanks for the clarification.
The error disappeared in the meantime…