fix: use _comp_compgen for multiline COMPREPLY=($(compgen ...))

[akinomyoga]

This is another round for _comp_compgen.

Also, word lists are re-folded on column 80 to fit the lines within 79 characters.

[scop]

Nice, pre-approved with some single vs double quote comments.

[scop]

(Maybe refactor or feat rather than fix for the commit messages though, your call.)

[akinomyoga]

(Maybe refactor or feat rather than fix for the commit messages though, your call.)

Actually, the rewriting using _comp_split/_comp_compgen (#948) has been originally planned for the protection against pathname expansions (failglob/nullglob) and word splitting (IFS), so they are fix in the sense that they solve the actual problems.

Edit: But I actually used refactor in the previous commit.