As task is a very generic name that conflicts with for example
taskwarrior, some packagers might choose to change it. See my package in
the AUR: https://aur.archlinux.org/packages/go-task.
This change makes it easier to configure the name for downstream
packagers.
1. 'compgen -c' lists _all_ command names on the system, which is not
appropriate for this script, furthermore echo does not read from stdin
so the output is lost.
2. use _get_comp_words_by_ref and __ltrim_colon_completions to handle task
names with colons.
"...modifying COMP_WORDBREAKS in your completion script is not safe
(as it is a global variable and it has the side effect of affecting
the behavior of other completion scripts"
Ref.: https://stackoverflow.com/a/12495727/7044304
3. Add options completion
4. Use task --list-all
