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

[akinomyoga]

These are relatively trivial ones for the _comp_compgen rewriting.

edit: #952 is blocking more, so could you see #952 before this? Merged

Note: The commits "fix: use _comp_compgen for COMPREPLY=(...)" are essentially generated by sed:

sed -E "s/$path/$rep/g"

with

pat='(COMPREPLY)=\(\$\(compgen ([^()]*) -- "\$(cur|\{cur-?\})"[[:space:]]*\)\)'   rep='_comp_compgen -- \2'
pat='(COMPREPLY)\+=\(\$\(compgen ([^()]*) -- "\$(cur|\{cur-?\})"[[:space:]]*\)\)' rep='_comp_compgen -a -- \2'
pat='(COMPREPLY)=\(\$\(compgen ([^()]*) -- ("[^"()]+")[[:space:]]*\)\)'           rep='_comp_compgen -c \3 -- \2'
pat='(COMPREPLY)\+=\(\$\(compgen ([^()]*) -- ("[^"()]+")[[:space:]]*\)\)'         rep='_comp_compgen -ac \3 -- \2'
pat='(COMPREPLY)=\(\$\(compgen ([^()]*)\)\)'                                      rep='_comp_compgen -R -- \2'
pat='(COMPREPLY)\+=\(\$\(compgen ([^()]*)\)\)'                                    rep='_comp_compgen -aR -- \2'

[akinomyoga]

• d660f8a In rebasing, I already found four oversights of -a that should not have been removed...

[akinomyoga]

The cases in f00dfd0 and ac88694 are the ones originally without specifying any -- "...". I suspect some of them were unintentionally forgotten to add -- "$cur".

• The completion generation for single characters such as -W '{0..9}' is fine without -- "$cur" because any filtering using "$cur" would generate all or nothing.
• The generated completions containing $cur as a prefix would also be fine (feh, tar, wget, rcs), though some of them might need proper quoting against the -W splitting.
• xgamma appears to try to remove the beginning : intensionally.
• suspect hping2 (1[TAB] would not complete)
• sus lintian, useradd, usermod

[scop]

LGTM! Pre-approved with some comments addressed.